bcma: add locking around GPIO register accesses

The GPIOs are access through some registers in the chip common core.
We need locking around these GPIO accesses, all GPIOs are accessed
through the same registers and parallel writes will cause problems.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: http://patchwork.linux-mips.org/patch/4585
Acked-by: Florian Fainelli <florian@openwrt.org>

include/linux/bcma/bcma_driver_chipcommon.h

@@ -567,6 +567,9 @@ struct bcma_drv_cc {
 	int nr_serial_ports;
 	struct bcma_serial_port serial_ports[4];
 #endif /* CONFIG_BCMA_DRIVER_MIPS */
+
+	/* Lock for GPIO register access. */
+	spinlock_t gpio_lock;
 };
 
 /* Register access */