fastboot: Extend fastboot_set_reboot_flag with reboot reason

Extend fastboot_set_reboot_flag arguments with reboot reason so that
it could handle different reboot cases in future.

Signed-off-by: Roman Kovalivskyi <roman.kovalivskyi@globallogic.com>

include/fastboot.h

@@ -40,6 +40,14 @@ enum {
 	FASTBOOT_COMMAND_COUNT
 };
 
+/**
+ * Reboot reasons
+ */
+enum fastboot_reboot_reason {
+	FASTBOOT_REBOOT_REASON_BOOTLOADER,
+	FASTBOOT_REBOOT_REASONS_COUNT
+};
+
 /**
  * fastboot_response() - Writes a response of the form "$tag$reason".
  *
@@ -77,7 +85,7 @@ void fastboot_okay(const char *reason, char *response);
  * which sets whatever flag your board specific Android bootloader flow
  * requires in order to re-enter the bootloader.
  */
-int fastboot_set_reboot_flag(void);
+int fastboot_set_reboot_flag(enum fastboot_reboot_reason reason);
 
 /**
  * fastboot_set_progress_callback() - set progress callback