HACK: Fix compile error on newer GCC

This fixes:

error: call to undeclared function 'wled_flash_led_prepare'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
                rc = wled_flash_led_prepare(trigger, options, max_current);
Change-Id: I02958e1a979e4124cb283fda99649a3ef08db160

qcom/opensource/camera-kernel/drivers/cam_sensor_module/cam_flash/cam_flash_core.c

@@ -19,6 +19,8 @@ extern struct cam_flash_ctrl *g_flash_ctrl;
 struct cam_flash_frame_setting g_flash_data;
 #endif
 
+int wled_flash_led_prepare(struct led_trigger *trigger, int options, int *max_current);
+
 int cam_flash_led_prepare(struct led_trigger *trigger, int options,
 	int *max_current, bool is_wled)
 {