avcodec/x86/videodsp: Properly mark sse2 instructions in emulated_edge_mc x86 simd as such.

Should fix crashes or corrupt output on pre-SSE2 CPUs when they were
using SSE2-code (e.g. AMD Athlon XP 2400+ or Intel Pentium III) in
hfix or hvar single-edge (left/right) extension functions.

Tested-by: Ingo Brückl <ib@wupperonline.de>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>