V4L/DVB (3723): Avoid unnecessary firmware re-loads in or51132 frontend

As QAM_64, QAM_256, and QAM_AUTO all use the same firmware, switching
between these modulations doesn't require a firmware re-load.  This also
fixes a mishandled error condition, in which the firmware file is loaded
into the kernel, the clock mode is changed, but then the firmware upload
to the device fails.  The modulation change is aborted, but the clock
mode would still be changed.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Andrew de Quincey <adq_dvb@lidskialf.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>