x86: h264dsp: Fix link failure with optimizations disabled

With optimzations disabled compilers have trouble doing dead code
elimination on 'if (foo && 0)' expressions, while 'if (0 && foo)'
still works, so use the latter to avoid problems.

Bug-Id: 707
Merge commit '5ab03e41e553452118113d0c224fa32b325e45e5'

* commit '5ab03e41e553452118113d0c224fa32b325e45e5':
  x86: h264dsp: Fix link failure with optimizations disabled

Merged-by: Michael Niedermayer <michaelni@gmx.at>