[media] cx25821,medusa: incorrect check on decoder type

Unsupported requests should be ignored but in fact affected VDEC_A

Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=44051

Reported-by:  <dcb314@hotmail.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Palash Bandyopadhyay <Palash.Bandyopadhyay@conexant.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>