Revert "GlobalISel: Use MMO helper for getting the size in bits"

This reverts commit dc98adf.

This should still be done, but this is currently causing some commit
ordering issues.

llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp

@@ -352,7 +352,8 @@ LegalizerInfo::getAction(const MachineInstr &MI,
 
   SmallVector<LegalityQuery::MemDesc, 2> MemDescrs;
   for (const auto &MMO : MI.memoperands())
-    MemDescrs.push_back({MMO->getSizeInBits(), 8 * MMO->getAlign().value(),
+    MemDescrs.push_back({8 * MMO->getSize() /* in bits */,
+                         8 * MMO->getAlign().value(),
                          MMO->getSuccessOrdering()});
 
   return getAction({MI.getOpcode(), Types, MemDescrs});