mfd: Remove check for db8500 firmware bug

In prcmu firmware version 3.4.4 the issue with longer
intervalls than 131 s was fixed, we don't expect the
issue to creep back up.

Signed-off-by: Jonas Aaberg <jonas.aberg@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>