[ARM][clang] Add back branch protection tests

When committing the PACBTI-M frontend support
patch (https://reviews.llvm.org/D112421), the tests in
arm-invalid-branch-protection.c were failing on certain test setups, so it was
removed to make the llvm test suite pass. The fix is to require
arm-registered-target.

This patch is part of a series that adds support for the PACBTI-M extension of
the Armv8.1-M architecture, as detailed here:

https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/armv8-1-m-pointer-authentication-and-branch-target-identification-extension

The PACBTI-M specification can be found in the Armv8-M Architecture Reference
Manual:

https://developer.arm.com/documentation/ddi0553/latest

Reviewed By: erichkeane

Differential Revision: https://reviews.llvm.org/D115141