media: video: Fix build in saa7164

-tip testing found that the x86 build (64-bit allyesconfig) fails due to:

  LD      vmlinux.o
  drivers/built-in.o:(.bss+0x4b648): multiple definition of `debug'
  arch/x86/built-in.o:(.kprobes.text+0x88): first defined here
  ld: Warning: size of symbol `debug' changed from 90 in
arch/x86/built-in.o to 4 in drivers/built-in.o
 make: *** [vmlinux.o] Error 1

This is because recent saa7164 changes introduced a global symbol
named 'debug'. The x86 platform code already defines a 'debug'
symbol. (which is named in a too generic way as well - but it
can be used nicely to weed out too generic symbols in drivers ;-)

Rename it to saa_debug.

[mchehab@redhat.com: use module_param_named to preserve old name]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>