mx25pdk: Add generic board support

Let's enable CONFIG_SYS_GENERIC_BOARD in order to get rid of warnings related
to generic board support is not in place.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>

include/configs/mx25pdk.h

@@ -14,6 +14,7 @@
 #define CONFIG_MX25
 #define CONFIG_SYS_TEXT_BASE		0x81200000
 #define CONFIG_MXC_GPIO
+#define CONFIG_SYS_GENERIC_BOARD
 
 #define CONFIG_SYS_TIMER_RATE		32768
 #define CONFIG_SYS_TIMER_COUNTER	\