i40e: Check if the BAR size is large enough before writing to registers

This patch fixes the problem with a kernel panic occurring when trying
to bind the i40e driver to a non-i40e port. The problem is fixed by
checking if the BAR size in the device is large enough by reading the
highest register.

Signed-off-by: Adam Ludkiewicz <adam.ludkiewicz@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>