[SCEV] NFC : Removing unnecessary check on outgoing branches of a branch instr.
For a given loop, getLoopLatch returns a non-null value
when a loop has only one latch block. In the modified
context a check on both the outgoing branches of a terminator instruction (of latch) to same header is redundant.
Reviewed By: jbhateja
Differential Revision: https://reviews.llvm.org/D40460