ARM: imx_v4_v5_defconfig: Enable initramfs support

This makes it possible to automatically boot-test this defconfig with
kernelci.org.
Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/configs/imx_v4_v5_defconfig

@@ -6,6 +6,7 @@ CONFIG_NO_HZ=y
 CONFIG_HIGH_RES_TIMERS=y
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CGROUPS=y
+CONFIG_BLK_DEV_INITRD=y
 CONFIG_EXPERT=y
 # CONFIG_COMPAT_BRK is not set
 CONFIG_SLAB=y