[AArch64] Simplify code in LowerGlobalAddress. NFCI.

When initial support for dllimport was added for aarch64 in
SVN r316555, ClassifyGlobalReference didn't set the MO_DLLIMPORT
flag - that was only completed in SVN r323810. Reuse the return
value from ClassifyGlobalReference for this purpose as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341310 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed