common/sfc_efx/base: add NIC magic check on BAR lookup
common/sfc_efx/base: add NIC magic check on BAR lookup

Check that BAR lookup was successful by looking at the content
of signature register.

Signed-off-by: Igor Romanov <945ea196dab32ad63762a1b623439a95515e898a@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <ac94ab2a8fe9a9a087f6e24dcbc16626b52c07e8@solarflare.com>
Reviewed-by: Andy Moreton <adbee5d9b6a6a553b71b14302d03837591e26c9d@xilinx.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk