media: cx23885: Override 888 ImpactVCBe crystal frequency

Hauppauge produced a revision of ImpactVCBe using an 888,
with a 25MHz crystal, instead of using the default third
overtone 50Mhz crystal. This overrides that frequency so
that the cx25840 is properly configured. Without the proper
crystal setup the cx25840 cannot load the firmware or
decode video.

Signed-off-by: Brad Love <brad@nextdimension.cc>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>