sparc32: Un-btfixup PAGE_{NONE,COPY,READONLY,SHARED,KERNEL}.

That lets us also get rid of the run-time initialization of
protection_map[] and all the ugly module workarounds for
PAGE_KERNEL and PAGE_SHARED to deal with the fact that we
can't do btfixups for modular code.

Signed-off-by: David S. Miller <davem@davemloft.net>