(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.

llvm-svn: 7334