Revert "word-at-a-time: make the interfaces truly generic This changes the interfaces in <asm/word-at-a-time.h> to be a bit more complicated, but a lot more generic."

This reverts commit 19e9834acbaa7dc42994562a462d005a76b0330b.
Revert "lib: Sparc's strncpy_from_user is generic enough, move under lib/ To use this, an architecture simply needs to:"

This reverts commit 4506dc6209d4a4e561fe3e3446060ac3258fb6d1.