[AArch64] Mark function calls as possibly changing FPCR

This patch does the same changes as D111433 for PowerPC and D139549 for
X86, - in the strictfp function all calls are marked as implicit defs of
FPCR. It prevents from moving FP operations across function calls, which
may change rounding mode, as fesetround does.

Differential Revision: https://reviews.llvm.org/D143001