ata: ahci-pci: Add new option CONFIG_SPL_AHCI_PCI

This new option allows to disable ahci-pci driver in SPL. Disabling it is
needed when SPL_PCI is not enabled as ahci-pci depends on PCI.

This change fixes following compile error when CONFIG_SPL_SATA_SUPPORT is
enabled and SPL_PCI is disabled.

    LD      spl/u-boot-spl
  arm-linux-gnueabihf-ld.bfd: drivers/ata/ahci.o: in function `ahci_probe_scsi_pci':
  drivers/ata/ahci.c:1205: undefined reference to `dm_pci_map_bar'
  arm-linux-gnueabihf-ld.bfd: drivers/ata/ahci.c:1215: undefined reference to `dm_pci_read_config16'
  arm-linux-gnueabihf-ld.bfd: drivers/ata/ahci.c:1216: undefined reference to `dm_pci_read_config16'
  arm-linux-gnueabihf-ld.bfd: drivers/ata/ahci.c:1220: undefined reference to `dm_pci_map_bar'
  make[1]: *** [scripts/Makefile.spl:512: spl/u-boot-spl] Error 1
  make: *** [Makefile:1977: spl/u-boot-spl] Error 2

    LD      spl/u-boot-spl
  arm-linux-gnueabihf-ld.bfd: drivers/ata/ahci-pci.o: in function `ahci_pci_probe':
  drivers/ata/ahci-pci.c:21: undefined reference to `ahci_probe_scsi_pci'
  make[1]: *** [scripts/Makefile.spl:512: spl/u-boot-spl] Error 1
  make: *** [Makefile:1977: spl/u-boot-spl] Error 2

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>