[LSR] Rewrite misses some fixup locations if it splits critical edge
If LSR split critical edge during rewriting phi operands and
phi node has other pending fixup operands, we need to
update those pending fixups. Otherwise formulae will not be
implemented completely and some instructions will not be eliminated.
Differential Revision: https://reviews.llvm.org/D60645
Patch by: Denis Bakhvalov <email@example.com>