ARM: mvebu: add MTD_BLOCK to mvebu_v7_defconfig

Since many (most?) mvebu platforms have NAND or SPI flashes, it makes
sense to have CONFIG_MTD_BLOCK=y in mvebu_v7_defconfig. The vast
majority of the other ARM defconfigs have it enabled, including
mvebu_v5_defconfig.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lkml.kernel.org/r/1415873489-22446-1-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>