[AArch64] BZ #16169 Add CFI directives to clone.S

[BZ #16169] Add CFI directives to the AArch64 clone.S implementation
and ensure that the FP in the child is zero'd in order to comply with
AAPCS.
(cherry picked from commit 3a3acb6afc753475675b5724f206e619d0c9590d)

Conflicts:

	NEWS