[RyuJIT/ARM32] Implement storing multi-reg/HFA return value at caller (dotnet/coreclr...

[RyuJIT/ARM32] Implement storing multi-reg/HFA return value at caller (dotnet/coreclr#12294)

* [RyuJIT/ARM32] Initial implementation of multi-reg return

Signed-off-by: Hyung-Kyu Choi <hk0110.choi@samsung.com>
* [RyuJIT/ARM32] Update multi-reg return for ARM32

- Update comment
- Remove wrong implementation
- Handle HFA struct correctly by consitering type

Signed-off-by: Hyung-Kyu Choi <hk0110.choi@samsung.com>
* Update comments for GetABIReturnReg() and GetABIReturnRegs()

- Remove and update obsolete comment
- Fix format

Signed-off-by: Hyung-Kyu Choi <hk0110.choi@samsung.com>
Commit migrated from https://github.com/dotnet/coreclr/commit/cf63336cbc2597801d62e399be6bdba8938d1034