imx: Make imx25 compatible to mxc_gpio driver and fix in tx25

Adding support for mxc_gpio driver for imx25 and fix names of registers in tx25
board.

Signed-off-by: Matthias Weisser <weisserm@arcor.de>
diff --git a/include/mxc_gpio.h b/include/mxc_gpio.h
index 002ba61..f673dce 100644
--- a/include/mxc_gpio.h
+++ b/include/mxc_gpio.h
@@ -24,6 +24,11 @@
 #ifndef __MXC_GPIO_H
 #define __MXC_GPIO_H
 
+/* Converts a GPIO port number and the internal bit position
+ * to the GPIO number
+ */
+#define MXC_GPIO_PORT_TO_NUM(port, bit) (((port - 1) << 5) + (bit & 0x1f))
+
 enum mxc_gpio_direction {
 	MXC_GPIO_DIRECTION_IN,
 	MXC_GPIO_DIRECTION_OUT,