mfd: Fix twl_has_pwrbutton typo

Change the typo CONFIG_INPUT_TWL4030_PWBUTTON_MODULE in the
twl_has_pwrbutton definition to CONFIG_INPUT_TWL4030_PWRBUTTON_MODULE.

Signed-off-by: Eduardo Valentin <eduardo.valentin@nokia.com>
Signed-off-by: Christoph Egger <siccegge@stud.informatik.uni-erlangen.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>