[PATCH] dvb: ttpci: more error handling for firmware communication

o propagate more errors back to caller or log them, mainly in
  av7110.c and av7110_av.c
o fix error message in StartHWFilter
o do not StopHWFilter for handle 0xffff

Signed-off-by: Wolfgang Rohdewald <wolfgang@rohdewald.de>
Signed-off-by: Johannes Stezenbach <js@linuxtv.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>