sgi-xp: remove redundant pointers ch and rp

The pointers ch and rp are set but are never used hence they are
redundant and can be removed.

Cleans up clang warnings:
warning: variable 'ch' set but not used [-Wunused-but-set-variable]
warning: variable 'rp' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>