PR25249, Memory leak in microblaze-dis.c

PR25249, Memory leak in microblaze-dis.c

	PR 25249
	* microblaze-dis.c (NUM_STRBUFS, STRBUF_SIZE): Define.
	(struct string_buf): New.
	(strbuf): New function.
	(get_field): Use strbuf rather than strdup of local temp.
	(get_field_imm, get_field_imm5, get_field_imm5_mbar): Likewise.
	(get_field_rfsl, get_field_imm15): Likewise.
	(get_field_rd, get_field_r1, get_field_r2): Update macros.
	(get_field_special): Likewise.  Don't strcpy spr.  Formatting.
	(print_insn_microblaze): Formatting.  Init and pass string_buf to
	get_field functions.