configs/roc_pc_rk3399_defconfig: expand rootfs size to 120M

Default 60M for rootfs are not enough and generate a build failure, so
let's expand rootfs size to 120M.

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
(cherry picked from commit 5194113331b04c5fee1a773e1751b40bff6fdd18)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/roc_pc_rk3399_defconfig

@@ -45,7 +45,7 @@ BR2_TARGET_GENERIC_HOSTNAME="roc-rk3399-pc"
 BR2_TARGET_GENERIC_ISSUE="Welcome to ROC-RK3399-PC!"
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
-BR2_TARGET_ROOTFS_EXT2_SIZE="64M"
+BR2_TARGET_ROOTFS_EXT2_SIZE="120M"
 BR2_PACKAGE_HOST_DOSFSTOOLS=y
 BR2_PACKAGE_HOST_GENIMAGE=y
 BR2_PACKAGE_HOST_MTOOLS=y