Address sanitizer reports error when rbp regitser is modified.
Register rbp was stored with rs_a which was used during prefetch
of Matrix A. Usage of rbp is avoided by using rcx register as a
temporary storage register.
Hence rcx is updated with Matrix C address before storing the
computed data.
This fix address the issue reported by GEQP3 API of libflame
AMD-Internal: [CPUPL-2587]
Change-Id: Ica790259010d8e71528c3d0ab1cd49069c56fc1d