Remove the TRI::getSubRegisterRegClass() hook.
Remove the TRI::getSubRegisterRegClass() hook.

This restores my karma after I added TRI::getSubClassWithSubReg().

Register constraints are applied 'backwards'.  Starting from the
register class required by an instruction operand, the correct question
is: 'How can I constrain the super-register register class so all its
sub-registers satisfy the instruction constraint?' The
getMatchingSuperRegClass() hook answers that.

We never need to go 'forwards': Starting from a super-register register
class, what register class are the sub-registers in?  The
getSubRegisterRegClass() hook did that.

git-svn-id: a4a6f32337ebd29ad4763b423022f00f68d1c7b7@141258 91177308-0d34-0410-b5e6-96231b3b80d8

lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx