[dev/lib][warnings] fix -Wmissing-declarations warnings in dev/ and lib/

dev/timer/arm_cortex_a9/arm_cortex_a9_timer.c

@@ -67,7 +67,7 @@ static struct fp_32_64 timer_freq_msec_conversion_inverse;
 
 static void arm_cortex_a9_timer_init_percpu(uint level);
 
-uint64_t get_global_val(void) {
+static uint64_t get_global_val(void) {
     uint32_t lo, hi;
 
 retry:

dev/timer/arm_generic/arm_generic_timer.c

@@ -5,6 +5,7 @@
  * license that can be found in the LICENSE file or at
  * https://opensource.org/licenses/MIT
  */
+#include <dev/timer/arm_generic.h>
 
 #include <arch/ops.h>
 #include <assert.h>