i40e/base: wrap the register definitions for PF and VF

i40e/base: wrap the register definitions for PF and VF

There were quite a few issues when the wrong defines were getting used
in the VF driver. This patch defines a new #define PF_DRIVER.
All the PF specific register definitions are wrapped in it.

The drivers will have to be updated to use the define in the PF
driver builds. Makes for a very short register.h for VF drivers.

Also fixes the code where PF driver register fields were getting used for
VF driver.

Signed-off-by: Jingjing Wu <jingjing.wu@intel.com>
Acked-by: Helin Zhang <helin.zhang@intel.com>
Tested-by: Huilong Xu <huilongx.xu@intel.com>