Fix regression introduced in r235816.
r235816 triggered kernel panic or hang after warm boot.
Don't blindly restore BCE_EMAC_MODE media configuration in
bce_reset().  If driver is about to shutdown it will invoke
bce_reset() which in turn results in restoring BCE_EMAC_MODE
media configuration.  This operation seems to confuse controller
firmware.

Reported by:	Paul Herman (herman <> cleverbridge dot com)
Tested by:	sbruno, Paul Herman (herman <> cleverbridge dot com)