ARM: OMAP2+ smsc911x: Fix possible stale smsc911x flags

If this function is called the first time with flags set, and the
second time without flags set then the leftover flags from the first
called will be used rather than the desired default flags.

Signed-off-by: Russ Dill <russ.dill@ti.com>
Tested-by: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Tony Lindgren <tony@atomide.com>