Input: surface3_spi - make const array header static, reduces object code size

Don't populate the const array header on the stack, instead make it
static.  Makes the object code smaller by over 180 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
   6003	   1536	      0	   7539	   1d73	surface3_spi.o

After:
   text	   data	    bss	    dec	    hex	filename
   5726	   1632	      0	   7358	   1cbe	surface3_spi.o

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/surface3_spi.c

@@ -173,7 +173,7 @@ static void surface3_spi_process_pen(struct surface3_ts_data *ts_data, u8 *data)
 
 static void surface3_spi_process(struct surface3_ts_data *ts_data)
 {
-	const char header[] = {
+	static const char header[] = {
 		0xff, 0xff, 0xff, 0xff, 0xa5, 0x5a, 0xe7, 0x7e, 0x01
 	};
 	u8 *data = ts_data->rd_buf;