bnxt_en: Prepare bnxt_init_one() to be called multiple times.

In preparation for the new firmware reset feature, some of the logic
in bnxt_init_one() and related functions will be called again after
firmware has reset.  Reset some of the flags and capabilities so that
everything that can change can be re-initialized.  Refactor some
functions to probe firmware versions and capabilities.  Check some
buffers before allocating as they may have been allocated previously.

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