[AArch64] Fix a typo in isExtFreeImpl()

next => not

Differential Revision: https://reviews.llvm.org/D36104

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309748 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed