[media] cx88: implemented sharpness control

This patch implements support for a sharpness control, using the luma
peaking filter feature of cx2388x.

[mchehab@redhat.com: use cx_andor instead of cx_write]
Signed-off-by: Istvan Varga <istvan_v@mailbox.hu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>