Revert "ARM: prefetch: add support for prefetchw using pldw on SMP ARMv7+ CPUs"

This reverts commit 2046950b60c52698964f2a466a83efb11d85fef0.
Revert "ARM: prefetch: remove redundant "cc" clobber"

This reverts commit 516671c9133b1f8d61a6fdccae84585e3d498b08.