Fix a number of incorrect intmath.h #includes.
Remove unnecessary dsputil.h #includes
configure: icc: Drop nonsense adding of cpuflags to LDFLAGS

This fixes many icc warnings when not setting the CPU type.
x86: dsputil_mmx: Remove leftover inline assembly fragments

These became unused in 71155d7b.

Signed-off-by: Martin Storsjö <martin@martin.st>