davinci: use divide ratio limits from pll_data

This patch modifies the sysclk rate setting code to use the divider mask
specified in pll_data.  Without this, devices with different divider ranges
(e.g. tnetv107x) fail.

Signed-off-by: Cyril Chemparathy <cyril@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>