math/clp: fix build on non-x86 non-ARM

Only amd64 and i386 have immintrin.h. There's a check for ARM, but not for other architectures.

Building without immintrin.h works fine on amd64.

PR: 242966
Approved by: co9co9@gmail.com (maintainer timeout)
MFH: 2020Q1 (fix build blanket)