bnxt_en: Refactor the HWRM_VER_GET firmware calls

Refactor the code so that __bnxt_hwrm_ver_get() does not call
bnxt_hwrm_do_send_msg() directly.  The new APIs will not expose this
internal call.  Add a new bnxt_hwrm_poll() to poll the HWRM_VER_GET
firmware call silently.  The other bnxt_hwrm_ver_get() function will
send the HWRM_VER_GET message directly with error logs enabled.

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