It seems PA7200 processors also suppress traps on loads to
%r0. This means we can prefetch for read on these cpus. Of course,
we can't support prefetch for write, since that requires
LOAD DOUBLEWORD which was added with PA2.0

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

asm/processor.h on parisc wants spinlocks for cpuinfo, but
linux/spinlock_types.h needs lockdep, and lockdep wants prefetch.

This leads to a horrible circular dependancy, because <asm/processor.h>
is including something which depends on things which are not defined
until the end of the file.

Kludge around this by moving prefetch related code into <asm/prefetch.h>
and including it before <linux/spinlock_types.h>, however this is just
a temporary solution until this mess can be cleaned up.

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>