V4L/DVB (9724): cx18: Streamline cx18-io[ch] wrappers and enforce MMIO retry strategy

cx18: Streamline cx18-io[ch] wrappers and enforce MMIO retry strategy so that
write retries always occur and read retries never occur (as they never help).
Remove MMIO statistics logging to speed up MMIO accesses.  Deprecate & ignore
retry_mmio and mmio_ndelay module parameters, to essentially force
retry_mmio=1 and mmio_ndelay=0.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>