[SCSI] fcoe: fix configuration problems

fcoe selects libfc and requires SCSI and PCI (the SCSI requirement is
implicitly covered by an enclosing if).  Fix them both up so they
cannot be configured in an invalid state: make LIBFC select
SCSI_FC_ATTRS and make FCOE depend on PCI and select LIBFC.

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>