V4L/DVB (4067): Fixed cx25840 to work with PAL/M

Sub-carrier frequency for PAL/M is slicely different than NTSC/M.
Without this patch, colors don't work on PAL/M.
Setting method also improved to allow other video standards to be included.

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