[media] si2168: Support Si2168-A20 firmware downloading

This adds support for the Si2168-A20 firmware download.

Extracting the firmware:

wget http://www.tbsdtv.com/download/document/tbs6281/tbs6281-t2-t-driver_v1.0.0.6.zip


unzip tbs6281-t2-t-driver_v1.0.0.6.zip
dd if=tbs-6281_x64/tbs6281_64.sys of=dvb-demod-si2168-a20-01.fw count=28656 bs=1 skip=1625088

md5sum:
32e06713b33915f674bfb2c209beaea5 /lib/firmware/dvb-demod-si2168-a20-01.fw

Signed-off-by: Luis Alves <ljalvs@gmail.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>