Remove LSR's use of the random AddrMode struct. These variables were
already in a class, just inline the four of them. I suspect that this
class could be simplified some to not always keep distinct variables for
these things, but it wasn't clear to me how given the usage so I opted
for a trivial and mechanical translation.

This removes one of the two remaining users of a header in include/llvm
which does nothing more than define a 4 member struct.