AArch64: Remove unused operand SM3_IMM2.
Removes the unused `SM3_IMM2` operand from the AArch64 assembler.
The SM3_IMM2 operand was intended for sm3tt* instructions in the AArch64 assembler, but these instructions were implemented using the Em operand instead. This commit removes the unused SM3_IMM2 operand, simplifying the code and removing a potential source of confusion.
In Details
The AARCH64_OPND_SM3_IMM2 operand was defined but unused in the AArch64 assembler. It was intended for the sm3tt* instructions, which ended up using AARCH64_OPND_Em instead. The operand is removed from gas/config/tc-aarch64.c, include/opcode/aarch64.h, opcodes/aarch64-asm-2.c, opcodes/aarch64-dis-2.c, opcodes/aarch64-opc-2.c, opcodes/aarch64-opc.c, and opcodes/aarch64-tbl.h.
For Context
The GNU Assembler (GAS) translates assembly code into machine code. This commit removes an unused operand definition from the AArch64-specific part of the assembler. This simplifies the codebase by removing parts that aren't used.