devel/llvm13: arm and aarch64 improvements

Change clang to allow -m32 on arm64. This is a backport from upstream
and will be merged to FreeBSD head soon. See D40943 for more info.

Remove an obsolete patch which breaks arm64. [0]

When BE_NATIVE is specified on aarch64, include the ARM (32-bit)
backend.

PR: 271616 [0]
Reported by: jfc@mit.edu [0]