[SCSI] fcoe: Use percpu kernel funcs for struct fcoe_percpu_s

Convert fcoe_percpu array to use the per-cpu variables
that the kernel provides. Use the kernel's functions to
access this structure.

The cpu member of the fcoe_percpu_s is no longer needed,
so this patch removes it too.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>