Fix art_quick_instrumentation_entry stub for x86/x86_64

Fixes bad stack offset for x86 where we read the return pc from an
incorrect location.

Fixes bad register for x86_64. The return pc is the 4th argument of
the called C function. It must be passed in rcx instead of r8 (which
is used for 5th argument).

Bug: 18170596
Change-Id: Idb521d2f6da415448fa61acf8b7d21076822830f