media: cx23885: add simple suspend/resume

After suspend-to-memory or suspend-to-disk, additional chips are no longer
reachable via i2c. Trying to tune to DVB-C on a cx23885 based
Hauppauge WinTV-HVR-4400-HD:

  si2165 8-0064: could not set chip_mode
  tda18271: performing RF tracking filter calibration

This patch implements the simplest possible suspend/resume that is
enough to tune to dvb-c channel after resume.
Afterwards dmesg looks like this:

  si2165 8-0064: downloading firmware from file 'dvb-demod-si2165.fw' \
    size=5768
  si2165 8-0064: si2165_upload_firmware: extracted patch_version=0x9a, \
    block_count=0x27, crc_expected=0xcc0a
  si2165 8-0064: fw load finished
  tda18271: performing RF tracking filter calibration
  tda18271: RF tracking filter calibration complete

Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>