[ARM] Don't confuse the scheduler for very large VLDMDIA etc.

ARMBaseInstrInfo::getNumLDMAddresses is making bad assumptions about the
memory operands of load and store-multiple operations.  This doesn't
really fix the problem properly, but it's enough to prevent crashing,
at least.

Fixes https://bugs.llvm.org/show_bug.cgi?id=41231 .

Differential Revision: https://reviews.llvm.org/D59834

llvm-svn: 357109