mfd: Fix twl_probe section mismatch warning in mfd/twl-core.c

Fix the following section mismatch warning when building
omap2plus_defconfig:

WARNING: vmlinux.o(.data+0x47d7c): Section mismatch in reference
from the variable twl_driver to the function .init.text:twl_probe()
Signed-off-by: NBryan Wu <bryan.wu@canonical.com>
Signed-off-by: NPaul Walmsley <paul@pwsan.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

drivers/mfd/twl-core.c

@@ -1003,7 +1003,7 @@ static int twl_remove(struct i2c_client *client)
 }
 
 /* NOTE:  this driver only handles a single twl4030/tps659x0 chip */
-static int __init
+static int __devinit
 twl_probe(struct i2c_client *client, const struct i2c_device_id *id)
 {
 	int				status;