mfd: twl6040: Fix sparse non static symbol warning

Fixes the following sparse warning:

drivers/mfd/twl6040.c:89:20: warning:
 symbol 'twl6040_patch' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/twl6040.c

@@ -86,7 +86,7 @@ static struct reg_default twl6040_defaults[] = {
 	{ 0x2E, 0x00 }, /* REG_STATUS	(ro) */
 };
 
-struct reg_default twl6040_patch[] = {
+static struct reg_default twl6040_patch[] = {
 	/* Select I2C bus access to dual access registers */
 	{ TWL6040_REG_ACCCTL, 0x09 },
 };