media: vidtv: fix build on 32bit architectures

Fix the following error for builds on 32bit architectures:

ERROR: modpost: "__udivdi3"
[drivers/media/test-drivers/vidtv/dvb-vidtv-bridge.ko] undefined!

Which is due to 64bit divisions that did not go through the helpers
in linux/math64.h

As vidtv_mux_check_mux_rate was not operational in its current form,
drop the entire function while it is not fixed properly.

For now, call vidtv_mux_pad_with_nulls with a constant number of packets
to avoid warnings due to unused functions when building this driver.

The 64bit division used in the s302m is not needed, remove them and use
a fixed number of frames and a constant PTS increment instead.

Fixes: f90cf607 ("media: vidtv: add a bridge driver")
Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>