ARM: configs: at91: Add mtd tests as modules

Add MTD tests as they are used in CI and for validation plan.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>

arch/arm/configs/at91_dt_defconfig

@@ -46,6 +46,7 @@ CONFIG_DEVTMPFS_MOUNT=y
 # CONFIG_STANDALONE is not set
 # CONFIG_PREVENT_FIRMWARE_BUILD is not set
 CONFIG_MTD=y
+CONFIG_MTD_TESTS=m
 CONFIG_MTD_CMDLINE_PARTS=y
 CONFIG_MTD_BLOCK=y
 CONFIG_MTD_DATAFLASH=y

arch/arm/configs/sama5_defconfig

@@ -55,6 +55,7 @@ CONFIG_DEVTMPFS_MOUNT=y
 # CONFIG_STANDALONE is not set
 # CONFIG_PREVENT_FIRMWARE_BUILD is not set
 CONFIG_MTD=y
+CONFIG_MTD_TESTS=m
 CONFIG_MTD_CMDLINE_PARTS=y
 CONFIG_MTD_BLOCK=y
 CONFIG_MTD_CFI=y