V4L/DVB (4701): Saa713x audio fixes

This change fixes the following issues:
- resolve the SECAM D/K vs SECAM-L sound conflict
  It is now possible to select the SECAM version either by the VIDEOIOC_S_STD
  IO control or by the new secam= insmod option.
  The driver now adapts its audio standard search list to the selected
  standard.
- don't trigger a sound standard search when a LINE input is selected.

Signed-off-by: Hartmut Hackmann <hartmut.hackmann@t-online.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>