[AArch64] Usage of FP regs whe only GP regs are allowed

[Evandro Menezes]

I noticed that when -mgeneral-regs-only FP registers are still used by the
LRA for spilling.  Though in rare cases I saw an ICE because of it, even
when it works it seems to me that the compiler should follow the desires of
its user.

I filed PR 62014 and posted there a patch to address this issue and restrict
the LRA from using FP registers if the user so desires.

I still need to come up with a suitable test-case to add, but I'd appreciate
any feedback.

Thanks,

-- 
Evandro Menezes                             Austin, USA
e.menezes@samsung.com                   +1-512-425-3365