x86/APX: widen @gotpcrel and @gottpoff support (incl to MOVRS)

x86/APX: widen @gotpcrel and @gottpoff support (incl to MOVRS)

If legacy-encoded arithmetic insns are eligible for @gotpcrel
relaxation, EVEX-encoded ones ought to be, too.

Further anything that MOV-from-memory can be used for (and transformed
from) should then also extend to MOVRS.

While extending the apx-load* testcases add  -mrelax-relocations=yes to
the two ones which were missing this: Without this option the intended
testing would not occur on configurations defaulting the option to off.