gas: sframe: add support for .cfi_negate_ra_state

gas: sframe: add support for .cfi_negate_ra_state

DW_CFA_AARCH64_negate_ra_state in aarch64 is multiplexed with
DW_CFA_GNU_window_save in the DWARF format.

Remove the common-empty-4 testcase because the generated SFrame section
will not be be empty anymore.  A relevant test will be added in a later
commit.

ChangeLog:

	* gas/gen-sframe.c (sframe_v1_set_fre_info): Add new argument
	for mangled_ra_p.
	(sframe_set_fre_info): Likewise.
	(output_sframe_row_entry): Handle mangled_ra_p.
	(sframe_row_entry_new): Reset mangled_ra_p.
	(sframe_row_entry_initialize): Initialize mangled_ra_p.
	(sframe_xlate_do_gnu_window_save): New definition.
	(sframe_do_cfi_insn): Handle DW_CFA_GNU_window_save.
	* gas/gen-sframe.h (struct sframe_row_entry): New member.
	(struct sframe_version_ops): Add a new argument for
	mangled_ra_p.
	* gas/testsuite/gas/cfi-sframe/cfi-sframe.exp: Remove test.
	* gas/testsuite/gas/cfi-sframe/common-empty-4.d: Removed.
	* gas/testsuite/gas/cfi-sframe/common-empty-4.s: Removed.