mfd: Use macros instead of some constant magic numbers for menelaus

This patch is originally done by Carlos Eduardo Aguiar. Original fix is
commit 3305829b2816072b9c8ed01374b205ae4de74027 in
git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6.git

Author modified the fix for mainline version of menelaus.

Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Cc: Carlos Eduardo Aguiar <carlos.aguiar@indt.org.br>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>