The pre_pll divisor must be such that ext_clk / pre_pll divisor does not
result in a frequency that is greater than pll_ip_clk_freq. Fix this.
Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>