[LoongArch] Explicitly specify instruction properties
This revision explicitly specifies the machine instruction properties instead of relying on guesswork. This is because guessing instruction properties has proven to be inaccurate, such as the machine LICM not working:
```
void func(char *a, char *b)
{
int i;
for (i = 0; i != 72526; i++)
a[i] = b[i];
}
```
Guessing instruction properties:
```
func: # @func
move $a2, $zero
.LBB0_1: # =>This Inner Loop Header: Depth=1
ldx.b $a3, $a1, $a2
stx.b $a3, $a0, $a2
addi.d $a2, $a2, 1
lu12i.w $a3, 17
ori $a3, $a3, 2894
bne $a2, $a3, .LBB0_1
ret
.Lfunc_end0:
```
Explicitly specify instruction properties:
```
func: # @func
lu12i.w $a2, 17
ori $a2, $a2, 2894
move $a3, $zero
.LBB0_1: # =>This Inner Loop Header: Depth=1
ldx.b $a4, $a1, $a3
stx.b $a4, $a0, $a3
addi.d $a3, $a3, 1
bne $a3, $a2, .LBB0_1
ret
.Lfunc_end0:
```
Reviewed By: SixWeining, xen0n
Differential Revision: https://reviews.llvm.org/D154192
f9e0845ef2