[AArch64] Install arm_neon_sve_bridge.h

arm_neon_sve_bridge.h is not generated, so the rules which ensure the
generated files get copied into the installation prefix don't apply to
this one.

Add it to the aarch64_only_files set instead, which ensures it ends up
both in the build directory and the installation directory.

Tested with build targets `clang-resource-headers` and
`install-clang-resource-headers`.

Differential Revision: https://reviews.llvm.org/D137239