V4L/DVB (3392a): XC3028 code removed from -git versions

- Current xc3028 support is still experimental, requiring more work to be
  sent to mainstream. It will be kept only at mercurial tree on
  http://linuxtv.org/hg

 until fixed.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>