Clang errors on a direct include of <bmi2intrin.h>
'Never use <bmi2intrin.h> directly; include <immintrin.h> instead.'
hit whenever __BMI2__ is defined.
Backport the upstream fix to include the umbrella <immintrin.h>
header guarded by an x86 check.
Signed-off-by: Khem Raj <raj.khem@gmail.com>