[media] drxk: Add a fallback method for QAM parameter setting

The QAM standard is set using this scu_command:
	SCU_RAM_COMMAND_STANDARD_QAM |
	SCU_RAM_COMMAND_CMD_DEMOD_SET_PARAM

The driver implements a version that has 4 parameters, however,
Terratec H5 needs to break this into two separate commands, otherwise,
DVB-C doesn't work.

With this fix, scan is now properly working and getting the
channel list:
>>> tune to: 609000000:INVERSION_AUTO:5217000:FEC_3_4:QAM_256
>>> tuning status == 0x00
>>> tuning status == 0x07
>>> tuning status == 0x1f

0x0093 0x0026: pmt_pid 0x0758 (null) -- SporTV2 (running, scrambled)
0x0093 0x0027: pmt_pid 0x0748 (null) -- SporTV (running, scrambled)
0x0093 0x0036: pmt_pid 0x0768 (null) -- FX (running, scrambled)
0x0093 0x0052: pmt_pid 0x0788 (null) -- The History Channel (running, scrambled)

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>