[warnings] remove some redundant declarations

Discovered with -Wredundant-decls

arch/arm/arm-m/include/arch/arm/cm.h

@@ -189,7 +189,6 @@ void arm_cm_irq_entry(void);
 void arm_cm_irq_exit(bool reschedule);
 
 /* built in exception vectors */
-void _start(void);
 void _nmi(void);
 void _hardfault(void);
 void _memmanage(void);

arch/arm/arm-m/start.c

@@ -15,7 +15,6 @@ extern unsigned int __data_start_rom, __data_start, __data_end;
 extern unsigned int __bss_start, __bss_end;
 
 /* entry point of the binary */
-void _start(void);
 void _start(void) {
     /* copy data from rom */
     if (&__data_start != &__data_start_rom) {

arch/arm/arm/thread.c

@@ -25,8 +25,6 @@ struct context_switch_frame {
     vaddr_t lr;
 };
 
-extern void arm_context_switch(addr_t *old_sp, addr_t new_sp);
-
 static void initial_thread_func(void) __NO_RETURN;
 static void initial_thread_func(void) {
     int ret;

arch/arm64/thread.c

@@ -34,8 +34,6 @@ struct context_switch_frame {
     vaddr_t r29;
 };
 
-extern void arm64_context_switch(addr_t *old_sp, addr_t new_sp);
-
 static void initial_thread_func(void) __NO_RETURN;
 static void initial_thread_func(void) {
     int ret;

arch/riscv/time.c

@@ -37,7 +37,6 @@ status_t platform_set_oneshot_timer (platform_timer_callback callback, void *arg
     // convert interval to ticks
     uint64_t ticks = riscv_get_time() + ((interval * ARCH_RISCV_MTIME_RATE) / 1000u);
 #if RISCV_M_MODE
-    extern void clint_set_timer(uint64_t ticks);
     clint_set_timer(ticks);
 #elif RISCV_S_MODE
     sbi_set_timer(ticks);

engine.mk

@@ -83,7 +83,7 @@ endif
 # flags that are sometimes nice to enable to catch problems but too strict to have on all the time.
 # add to global flags from time to time to find things, otherwise only available with a module
 # option (see make/module.mk re: MODULE_OPTIONS).
-EXTRA_MODULE_COMPILEFLAGS := -Wmissing-declarations
+EXTRA_MODULE_COMPILEFLAGS := -Wmissing-declarations -Wredundant-decls
 EXTRA_MODULE_CFLAGS := -Wmissing-prototypes
 EXTRA_MODULE_CPPFLAGS :=
 EXTRA_MODULE_ASMFLAGS :=
@@ -91,6 +91,7 @@ EXTRA_MODULE_ASMFLAGS :=
 #GLOBAL_COMPILEFLAGS += -Wpacked
 #GLOBAL_COMPILEFLAGS += -Wpadded
 #GLOBAL_COMPILEFLAGS += -Winline
+#GLOBAL_COMPILEFLAGS += -Wredundant-decls
 
 # if WERROR is set, add to the compile args
 ifeq (true,$(call TOBOOL,$(WERROR)))

external/platform/stm32f7xx/STM32F7xx_HAL_Driver/Inc/stm32f7xx_hal_nand.h

@@ -204,7 +204,7 @@ HAL_StatusTypeDef  HAL_NAND_GetECC(NAND_HandleTypeDef *hnand, uint32_t *ECCval,
   */
 /* NAND State functions *******************************************************/
 HAL_NAND_StateTypeDef HAL_NAND_GetState(NAND_HandleTypeDef *hnand);
-uint32_t              HAL_NAND_Read_Status(NAND_HandleTypeDef *hnand);
+//uint32_t              HAL_NAND_Read_Status(NAND_HandleTypeDef *hnand);
 /**
   * @}
   */

lib/minip/include/lib/minip.h

@@ -87,8 +87,6 @@ static inline status_t tcp_accept(tcp_socket_t *listen_socket, tcp_socket_t **ac
 
 /* utilities */
 void gen_random_mac_address(uint8_t *mac_addr);
-uint32_t minip_parse_ipaddr(const char *addr, size_t len);
-
 uint32_t minip_parse_ipaddr(const char *addr, size_t len);
 void printip(uint32_t x);
 void printip_named(const char *s, u32 x);