micrel: fix masking off LED bits

Commit 20d8435a (phy: micrel: add of configuration for LED mode) made the
obvious mistake when masking off  the LED mode bits: forgot to do a logical NOT
to the mask with which it ANDs the register value, so that unrelated bits are
cleared instead.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Ben Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>