[LoongArch64] Fix the NotImplementedException within R2RDump.

[shushanhf]

This PR is part of the issue #69705 to amend the LA's port.

Fix the NotImplementedException within R2RDump for LoongArch64.

[shushanhf]

@EgorBo
Could you give me some advices?

The R2RDump is OK for LoongArch64.

But the crossgen2 has some problem.
For the test readytorun/tests/mainv1/mainv1.sh, after the command $CORE_ROOT/corerun $CORE_ROOT/crossgen2/crossgen2.dll --map -r:$CORE_ROOT/*.dll -r:IL_DLLS/fieldgetter.dll -r:IL_DLLS/mainv1.dll -o:test.dll ../testv1/test/test.dll

The test.dll is still PE32 format.

file ~/tests/tests8_Debug0626/readytorun/tests/mainv1/test.dll
/home/qiao/tests/tests8_Debug0626/readytorun/tests/mainv1/test.dll:        PE32 executable (DLL) (console) Mono/.Net assembly, for MS Windows

While my local runtime6.0's crossgen2 is OK for LoongArch64.