remove memory in the clobber list because rdtsp is a serializing instr.
remove memory in the clobber list because rdtsp is a serializing instr.

stlankes/HermitCore,RWTH-OS/HermitCore,RWTH-OS/HermitCore,RWTH-OS/HermitCore,RWTH-OS/HermitCore,stlankes/HermitCore,stlankes/HermitCore,RWTH-OS/HermitCore,stlankes/HermitCore,stlankes/HermitCore,RWTH-OS/HermitCore,stlankes/HermitCore