scsi: fdomain: fix building pcmcia front-end

We get a warning when CONFIG_SCSI_LOWLEVEL is disabled here:

WARNING: unmet direct dependencies detected for SCSI_FDOMAIN
  Depends on [n]: SCSI_LOWLEVEL [=n] && SCSI [=y]
  Selected by [m]:
  - PCMCIA_FDOMAIN [=m] && SCSI_LOWLEVEL_PCMCIA [=y] && SCSI [=y] && PCMCIA [=y] && m && MODULES [=y]

Move all of SCSI_LOWLEVEL_PCMCIA inside of the existing SCSI_LOWLEVEL
section. Very few people use the PCMCIA support these days, and they likely
don't mind having to turn on SCSI_LOWLEVEL as well. This way we avoid the
link error and get a more sensible structure.

Fixes: 7d47fa065e62 ("scsi: fdomain: Add PCMCIA support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>