Fix ARMGlobalMerge pass to check if globals are entirely within range.

Fix ARMGlobalMerge pass to check if globals are entirely within range.
It is generally not sufficient to check if the starting offset is in range
of the maximum offset that can be efficiently used for the target.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119565 91177308-0d34-0410-b5e6-96231b3b80d8