[Statepoints] Allow deopt GC pointer on VReg if gc-live bundle is empty.

Currently we allow passing pointers from deopt bundle on VReg only if
they were seen in list of gc-live pointers passed on VRegs.
This means that for the case of empty gc-live bundle we spill deopt
bundle's pointers. This change allows lowering deopt pointers to VRegs
in case of empty gc-live bundle. In case of non-empty gc-live bundle,
behavior does not change.

Reviewed By: skatkov

Differential Revision: https://reviews.llvm.org/D88999