Remove "memory exhausted" messages

Since we use xcalloc to set up hash table memory, htab_create won't
ever return a failure.

	* config/tc-aarch64.c (md_begin): Don't bother checking for
	out of memory failure from str_htab_create.
	* config/tc-arc.c (arc_insert_opcode, md_begin): Likewise.
	(arc_extcorereg, arc_stralloc): Likewise.
	* config/tc-arm.c (md_begin): Likewise.
	* config/tc-cr16.c (initialise_reg_hash_table, md_begin): Likewise.
	* config/tc-cris.c (md_begin): Likewise.
	* config/tc-crx.c (md_begin): Likewise.
	* config/tc-pdp11.c (md_begin): Likewise.
	* config/tc-score.c (s3_build_reg_hsh, s3_begin): Likewise.
	* config/tc-score7.c (s7_build_reg_hsh, s7_begin): Likewise.