[arch][arm64] Remove unused variable
[arch][arm64] Remove unused variable

Change-Id: I9f36092a938642f96c9a8488e4fb35017be40f9d

minglun-tsai/lk,littlekernel/lk,travisg/lk,hollanderic/lkstuff,travisg/lk,ErikCorryGoogle/lk,minglun-tsai/lk,hollanderic/lkstuff,hollanderic/lkstuff,sndnvaps/lk,littlekernel/lk,ErikCorryGoogle/lk,littlekernel/lk,hollanderic/lkstuff,minglun-tsai/lk,ErikCorryGoogle/lk,sndnvaps/lk,travisg/lk,minglun-tsai/lk,travisg/lk,ErikCorryGoogle/lk,sndnvaps/lk,sndnvaps/lk,sndnvaps/lk,littlekernel/lk