[LoongArch] Fixed llvm/test/CodeGen/LoongArch/intrinsic.ll test failure when...

[LoongArch] Fixed llvm/test/CodeGen/LoongArch/intrinsic.ll test failure when EXPENSIV_CHECK is enabled [1].

Specifically:
```
*** Bad machine code: Using an undefined physical register ***
- function:    movgr2fcsr
- basic block: %bb.0 entry (0x1af5e60)
- instruction: MOVGR2FCSR $fcsr1, %0:gpr
- operand 0:   $fcsr1

*** Bad machine code: Using an undefined physical register ***
- function:    movfcsr2gr
- basic block: %bb.0 entry (0x133fae0)
- instruction: %0:gpr = MOVFCSR2GR $fcsr1
- operand 1:   $fcsr1
```

By building MachineInstructions, the state of the register is
clarified, and the error caused by using undefined physical registers
is fixed.

[1]: https://lab.llvm.org/buildbot/#/builders/16/builds/41677