gas: sframe: Fix typo in comment on SFrame identifier

gas/config/
	* tc-aarch64.c (aarch64_sframe_get_abi_arch): Fix typo in
	comment on SFrame identifier.
	* tc-aarch64.h (aarch64_sframe_get_abi_arch,
	sframe_get_abi_arch): Likewise.
	* tc-i386.c (x86_sframe_get_abi_arch): Likewise.
	* tc-i386.h (x86_sframe_get_abi_arch, sframe_get_abi_arch):
	Likewise.

Reported-by: Indu Bhagat <indu.bhagat@oracle.com>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>