bnxt_en: Call bnxt_ethtool_free() in bnxt_init_one() error path

bnxt_ethtool_init() may have allocated some memory and we need to
call bnxt_ethtool_free() to properly unwind if bnxt_init_one()
fails.

Fixes: 7c380918

 ("bnxt_en: Refactor bnxt_init_one() and turn on TPA support on 57500 chips.")
Signed-off-by: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>