(1) Major fix to the way unused regs. are marked and found for the FP

(1) Major fix to the way unused regs. are marked and found for the FP
    Single and FP double reg types (which share the same reg class).
    Now all methods marking/finding unused regs consider the regType
    within the reg class, and SparcFloatRegClass specializes this code.
(2) Remove machine-specific regalloc. methods that are no longer needed.
    In particular, arguments and return value from a call do not need
    machine-specific code for allocation.
(3) Rename TargetRegInfo::getRegType variants to avoid unintentional
    overloading when an include file is omitted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7334 91177308-0d34-0410-b5e6-96231b3b80d8