MIPS16: Remove unused `>' operand code

MIPS16: Remove unused `>' operand code

This code has never been used throughout the repository history, and
likely not before either, as due to the assymetry of MIPS16 instruction
set encoding there are no 32-bit shift operations having their immediate
shift count placed in the position of the usual `rx' instruction field.

	gas/
	* config/tc-mips.c (mips16_macro_build) <'>'>: Remove case.

	include/
	* opcode/mips.h: Remove references to `>' operand code.

	opcodes/
	* mips16-opc.c (decode_mips16_operand) <'>'>: Remove cases.