V4L/DVB (9599): cx18: Fix unitialized variable problem upon APU firmware file read failure

If APU firmware file read failed, the jump vector to the APU was undefined and
the APU would be started executing garbage.  Fix uninitialized variable to be
an infinite loop for the APU, but also bail out before even starting the APU.

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