drivers/misc/sgi-xp: Remove orphan declarations from drivers/misc/sgi-xp/xp.h

drivers/misc/sgi-xp: Remove orphan declarations from drivers/misc/sgi-xp/xp.h

Remove the following orphan declarations from drivers/misc/sgi-xp/xp.h:
1. xp_nofault_PIOR_target
2. xp_error_PIOR
3. xp_nofault_PIOR

They have been removed since commit f90c2919ec91 ("misc/sgi-xp:
remove SGI SN2 support"), so remove them.

Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Link: https://lore.kernel.org/r/20220913110356.764711-1-cuigaosheng1@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>