MIPS16/GAS: Fix forced size suffixes with argumentless instructions

MIPS16/GAS: Fix forced size suffixes with argumentless instructions

Correct the handling of `.e' and `.t' instruction size suffixes with
instruction mnemonics which are not followed by any text on the same
line, such as arguments or white space, e.g.:

$ cat test.s
	.set	mips16
foo:
	entry.t		# comment
	entry.t
	exit.t		# comment
	exit.t
	nop.t		# comment
	nop.t
$ as -32 -o test.o test.s
test.s: Assembler messages:
test.s:4: Error: unrecognized opcode `entry.t'
test.s:6: Error: unrecognized opcode `exit.t'
test.s:8: Error: unrecognized opcode `nop.t'
$

	gas/
	* config/tc-mips.c (mips16_ip): Handle `.e' and `.t' instruction
	suffixes followed by a null character rather than a space too.
	* testsuite/gas/mips/mips16-insn-length-noargs.d: New test.
	* testsuite/gas/mips/mips16-insn-length-noargs.s: New test
	source.
	* testsuite/gas/mips/mips.exp: Run the new test.