ARM: imx_v6_v7_defconfig: Increase CMA size

Increase the CMA size to 64 MiB, otherwise it isn't possible to use
etnaviv driver on systems with 1920x1080 panel due to insufficient
memory .
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -86,6 +86,7 @@ CONFIG_DEVTMPFS=y
 CONFIG_DEVTMPFS_MOUNT=y
 # CONFIG_STANDALONE is not set
 CONFIG_DMA_CMA=y
+CONFIG_CMA_SIZE_MBYTES=64
 CONFIG_IMX_WEIM=y
 CONFIG_CONNECTOR=y
 CONFIG_MTD=y