Since the word to byte register conversion isn't active for x86-64

Since the word to byte register conversion isn't active for x86-64
anyway, there's also no need to issue a separate, inconsistent
diagnostic in some of the cases - non-matching operands will be
complained about anyway.

2012-07-31  Jan Beulich <jbeulich@suse.com>

	* config/tc-i386.c (check_byte_reg): Check for I/O port
	register earlier, and just once. Drop diagnostic that got
	issued only for some registers.