V4L/DVB (12181): get_dvb_firmware: Add Yuan MPC718 MT352 DVB-T "firmware" extraction

Add routine to support extracting the MT352 DVB-T demodulator initialization
sequence for Yuan MPC718 cards for use by the cx18 driver.

This routine uses a hueristic for extracting a good sequence.  It should work
on all different versions of the "yuanrap.sys" file, given the way the MT352
tuning sequences are stored in all versions of that file I have seen so far.
However, the current patch simply looks for one specific archive URL.

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