bnxt_en: Cleanup and Fix flow control setup logic

Cleanup bnxt_probe_phy() to cleanly separate 2 code blocks for autoneg
on and off.  Autoneg flow control is possible only if autoneg is enabled.

In bnxt_get_settings(), Pause and Asym_Pause are always supported.
Only the advertisement bits change depending on the ethtool -A setting
in auto mode.

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