JitArm64: Skip redundant imm to register writes

When a guest register is an immediate, it may be necessary to move this
value into a register. This is handled by gpr.R(), which lacks context
on how the register will be used. This leads to cases where the
immediate is written to a register, only for it to be overwritten. Take
for example this code generated by srwx:

0x5280031b   mov    w27, #0x18
0x53187edb   lsr    w27, w22, #24

gpr.BindToRegister() does have this context through the do_load
parameter, but didn't handle immediates. By adding this logic, we can
intelligently skip the write when do_load is false.

Source/Core/Core/PowerPC/JitArm64/JitArm64_RegCache.cpp

@@ -362,6 +362,16 @@ void Arm64GPRCache::BindToRegister(const GuestRegInfo& guest_reg, bool do_load,
       m_emit->LDR(IndexType::Unsigned, host_reg, PPC_REG, u32(guest_reg.ppc_offset));
     }
   }
+  else if (reg_type == RegType::Immediate)
+  {
+    const ARM64Reg host_reg = bitsize != 64 ? GetReg() : EncodeRegTo64(GetReg());
+    if (do_load)
+    {
+      m_emit->MOVI2R(host_reg, reg.GetImm());
+    }
+    reg.Load(host_reg);
+    reg.SetDirty(set_dirty);
+  }
   else if (set_dirty)
   {
     reg.SetDirty(true);