lavc: define STRIDE_ALIGN as 32 when compiling with AVX support

Signed-off-by: James Almer <jamrial@gmail.com>
Reviewed-by: "Ronald S. Bultje" <rsbultje@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/ppc/asm: fix build with ABI v2

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