aarch64,arm: Remove accepted_branch_protection_string

aarch64,arm: Remove accepted_branch_protection_string

On aarch64 this caused ICE with pragma push_options since

  commit ae54c1b09963779c5c3914782324ff48af32e2f1
  Author:     Wilco Dijkstra <wilco.dijkstra@arm.com>
  CommitDate: 2022-06-01 18:13:57 +0100

  AArch64: Cleanup option processing code

The failure is at pop_options:

internal compiler error: ‘global_options’ are modified in local context

On arm the variable was unused.

gcc/ChangeLog:

	* config/aarch64/aarch64.cc (aarch64_override_options_after_change_1):
	Do not override branch_protection options.
	(aarch64_override_options): Remove accepted_branch_protection_string.
	* config/arm/aarch-common.cc (BRANCH_PROTECT_STR_MAX): Remove.
	(aarch_parse_branch_protection): Remove
	accepted_branch_protection_string.
	* config/arm/arm.cc: Likewise.