[NFC][AArch64] Rename SVE2p1 sclamp and uclamp tests

Both sclamp and uclamp are part of the SVE2p1 feature so I've
renamed the tests accordingly:

sve2-intrinsics-sclamp.ll -> sve2p1-intrinsics-sclamp.ll
sve2-intrinsics-uclamp.ll -> sve2p1-intrinsics-uclamp.ll