staging: sm750fb: simplify PLL divisors calculations

The calcPllValues currently uses arrays of PLL parametres that contain
possible PLL control register field values and redundant data that is
calculated according to those values. The usage of these arrays can be
replaced with simple arithmetics.

Signed-off-by: Mike Rapoport <mike.rapoport@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>