[bus][pci] trivially switch the PCI bus driver to c++

Just minimum to get it to build and work.

dev/bus/pci/debug.cpp

@@ -235,6 +235,3 @@ STATIC_COMMAND_START
 STATIC_COMMAND("pci", "pci toolbox", &pci_cmd)
 STATIC_COMMAND_END(pcitests);
 
-APP_START(pcitests)
-APP_END
-

dev/bus/pci/include/dev/bus/pci.h

@@ -11,6 +11,8 @@
 #include <sys/types.h>
 #include <lk/compiler.h>
 
+__BEGIN_CDECLS
+
 /*
  * PCI access return codes
  */
@@ -163,3 +165,4 @@ int pci_write_config_word(const pci_location_t *state, uint32_t reg, uint32_t va
 int pci_get_irq_routing_options(irq_routing_entry *entries, uint16_t *count, uint16_t *pci_irqs);
 int pci_set_irq_hw_int(const pci_location_t *state, uint8_t int_pin, uint8_t irq);
 
+__END_CDECLS

dev/bus/pci/rules.mk

@@ -3,9 +3,9 @@ LOCAL_DIR := $(GET_LOCAL_DIR)
 MODULE := $(LOCAL_DIR)
 
 MODULE_SRCS += \
-	$(LOCAL_DIR)/bios32.c \
-	$(LOCAL_DIR)/debug.c \
-	$(LOCAL_DIR)/pci.c \
-	$(LOCAL_DIR)/type1.c \
+	$(LOCAL_DIR)/bios32.cpp \
+	$(LOCAL_DIR)/debug.cpp \
+	$(LOCAL_DIR)/pci.cpp \
+	$(LOCAL_DIR)/type1.cpp \
 
 include make/module.mk