Quick: Remove broken Mir2Lir::LocToRegClass().

Its use in intrinsics has been bogus. In all other instances
it's been used under the assumption that the inferred type
matches the return type of associated calls. However, if the
type inference identifies a type mismatch, the assumption
doesn't hold and there isn't necessarily a valid value that
the function could reasonably return.

Bug: 19918641
Change-Id: I050934e6f9eb00427d0b888ee29ae9eeb509bb3f