[SCSI] aic79xx: fix warnings with CONFIG_PM disabled

  CC [M]  drivers/scsi/aic7xxx/aic79xx_osm_pci.o
drivers/scsi/aic7xxx/aic79xx_osm_pci.c:101: warning: 'ahd_linux_pci_dev_suspend' defined but not used
drivers/scsi/aic7xxx/aic79xx_osm_pci.c:121: warning: 'ahd_linux_pci_dev_resume' defined but not used

This moves aic79xx_pci_driver struct, removes some forward
declarations, and adds some ifdef CONFIG_PM.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>