dm mpath: hp requires scsi

With CONFIG_SCSI=n __scsi_print_sense() is never linked in.

drivers/built-in.o: In function `hp_sw_end_io':
dm-mpath-hp-sw.c:(.text+0x914f8): undefined reference to `__scsi_print_sense'

Caught with a randconfig on current git.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>