The cx25840 driver currently configures 885, 887, and 888 using
default divisors for each chip. This check to see if the cx23885
driver has passed the cx25840 a non-default clock rate for a
specific chip. If a cx23885 board has left clk_freq at 0, the
clock default values will be used to configure the PLLs.

This patch only has effect on 888 boards who set clk_freq to 25M.
Signed-off-by: Brad Love <brad@nextdimension.cc>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>