bnxt_en: Get firmware package version one time.

The current code retrieves the firmware package version from firmware
everytime ethtool -i is run.  There is no reason to do that as the
firmware will not change while the driver is loaded.  Get the version
once at init time.

Also, display the full 4-part firmware version string and remove the
less useful interface spec version.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>