[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.

llvm.org/PR41445

Differential Revision: https://reviews.llvm.org/D60645

Patch by: Denis Bakhvalov <denis.bakhvalov@intel.com>

llvm-svn: 358457