mfd: Fix 88pm860x uninitialized variable and clean up

The original code had a compile warning:
drivers/mfd/88pm860x-core.c:431: warning: ‘ret’ may be used
	uninitialized in this function
It seems like the warning is valid if either pdata or pdata->touch is
NULL.

This patch checks pdata and pdata->touch at the beginning of the
function.  That means everything can be pulled in one indent level.
Now all the statements fit within the 80 character limit.

Also at that point the "use_gpadc" variable isn't needed and removing
it simplifies the logic.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Haojian Zhuang <hzhuang1@marvell.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>