Input: pxa27x_keypad - remove an unneeded NULL check

Static checkers complain about this NULL check because we dereference it
without checking a couple lines later.  This function is only called
when "keypad->pdata" is non-NULL so we can just delete the NULL test.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
[Dmitry: remove the variable altogether given that it is used just once and
 dereference directly.]
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>