platform: msm_shared: add support for checking alarmboot mode

When the phone is triggered by alarm, it's required to turn off
the display during booting until the alarm app is invoked. So add
the function to check device if it's alarm boot.

Change-Id: I4eca894753dd47095dca93958a29c19476f42382
diff --git a/include/platform.h b/include/platform.h
index e71c407..2aa4c56 100644
--- a/include/platform.h
+++ b/include/platform.h
@@ -54,6 +54,7 @@
 unsigned board_platform_id(void);
 unsigned check_reboot_mode(void);
 unsigned check_hard_reboot_mode(void);
+uint32_t check_alarm_boot(void);
 void platform_uninit_timer(void);
 void reboot_device(unsigned);
 int set_download_mode(enum dload_mode mode);