i40e/base: support building both PF and VF driver together

i40e/base: support building both PF and VF driver together

Macros of PF_DRIVER, VF_DRIVER and INTEGRATED_VF were defined to
support building both PF and VF driver together. PF_DRIVER needs
to be defined if a build is for PF only, while VF_DRIVER for VF
only. PF_DRIVER, VF_DRIVER and INTEGRATED_VF are all needed for
building both PF and VF driver together.

Test report: http://www.dpdk.org/ml/archives/dev/2015-May/017384.html

Signed-off-by: Helin Zhang <helin.zhang@intel.com>
Acked-by: Jingjing Wu <jingjing.wu@intel.com>
Acked-by: Jijiang Liu <jijiang.liu@intel.com>
Tested-by: Min Cao <min.cao@intel.com>