b53: widen stp state mask to 3 bits (instead of 2)

At least on my b53 chip, the mask is 3 bits wide, and because
of this some STP states are not set properly and discarded when read.

Maybe for some other chips it makes sense to have just 2 bits width,
but I don't have other versions around to test/validate.

If that's the case then maybe we could add another STP state mask.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Jonas Gorski <jogo@openwrt.org>

SVN-Revision: 45937

target/linux/generic/files/drivers/net/phy/b53/b53_regs.h

@@ -65,7 +65,7 @@
 #define   PORT_CTRL_RX_MCST_EN		BIT(3) /* Multicast RX (P8 only) */
 #define   PORT_CTRL_RX_UCST_EN		BIT(4) /* Unicast RX (P8 only) */
 #define	  PORT_CTRL_STP_STATE_S		5
-#define   PORT_CTRL_STP_STATE_MASK	(0x3 << PORT_CTRL_STP_STATE_S)
+#define   PORT_CTRL_STP_STATE_MASK	(0x7 << PORT_CTRL_STP_STATE_S)
 
 /* SMP Control Register (8 bit) */
 #define B53_SMP_CTRL			0x0a