atm: solos-pci: make solos_bh() as static

sparse says:

drivers/atm/solos-pci.c:763:6: warning:
 symbol 'solos_bh' was not declared. Should it be static?

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Acked-by: Chas Williams <chas@cmf.nrl.navy.mil>
Signed-off-by: David S. Miller <davem@davemloft.net>