mfd: twl: Replace twl_has_*() macros by IS_ENABLED()

Instead of reinventing macros for the same purpose, use the standard
macros.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>