MIPS16/opcodes: Correct I64/SDRASP opcode's ISA membership

MIPS16/opcodes: Correct I64/SDRASP opcode's ISA membership

Limit the `SD ra, offset(sp)' instruction (I64/SDRASP major/minor
opcode) to the MIPS III rather than MIPS I ISA.  This is a 64-bit
instruction requiring a 64-bit ISA.  This bug has been there since
forever.

	opcodes/
	* mips16-opc.c (mips16_opcodes): Set membership to I3 rather
	than I1 for the SP-relative "sd"/$ra entry (SDRASP minor
	opcode).

	gas/
	* testsuite/gas/mips/mips16-sdrasp.d: New test.
	* testsuite/gas/mips/mips16-sdrasp.l: New stderr output.
	* testsuite/gas/mips/mips16-sdrasp.s: New test source.
	* testsuite/gas/mips/mips.exp: Run the new test.