ARM: mxs: enable flexcan on imx28

As the flexcan driver has DT binding for some time now. This patch makes
the flexcan driver available in the can drivers menu if a SOC with flexcan
is enabled.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-mxs/Kconfig

@@ -16,6 +16,7 @@ config SOC_IMX28
 	bool
 	select ARM_AMBA
 	select CPU_ARM926T
+	select HAVE_CAN_FLEXCAN if CAN
 	select HAVE_PWM
 	select PINCTRL_IMX28