DGNC is based on PCI, so need add related dependency, or when compiled
with PCI disabled, it will be fail.

The related error (randconfig for PCI disabled under s390):

  drivers/staging/dgnc/dgnc_cls.c:1394:2: error: implicit declaration of function ‘ioremap’ [-Werror=implicit-function-declaration]
  drivers/staging/dgnc/dgnc_cls.c:1407:3: error: implicit declaration of function ‘iounmap’ [-Werror=implicit-function-declaration]

Cc: Lidza Louina <lidza.louina@gmail.com>
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>