[asan] Remove unnecessary spill in optimized callbacks

We can use r11 scratch registers for calculations.

It does not result in any performance improvements, as the spill is on
the slow path of partial granules.

See X86AsmPrinter::LowerASAN_CHECK_MEMACCESS for callers.

Reviewed By: kstoimenov

Differential Revision: https://reviews.llvm.org/D158525