Remove unused varible

The Result variable is unused both in Sema::CheckARMBuiltinFunctionCall
and Sema::CheckAArch64BuiltinFunctionCall, remove it.

Patch by Wei-Ren Chen!

Reviewers: craig.topper, rnk

Reviewed By: rnk

Subscribers: aemerson, cfe-commits, rengolin

Differential Revision: https://reviews.llvm.org/D32014

llvm-svn: 300572