configs/roseapplypi_defconfig: really change to ext4 rootfs

Commit b8aebcfd823f83c16 (configs/roseapplypi_defconfig: bump kernel to
5.15.10) adjusted the board to use an ext4 rootfs, but forgot to update the
defconfig to enable ext4 rootfs, breaking the build. Correct that.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

configs/roseapplepi_defconfig

@@ -21,7 +21,8 @@ BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="owl-s500-roseapplepi"
 
 # Filesystem / image
-BR2_TARGET_ROOTFS_INITRAMFS=y
+BR2_TARGET_ROOTFS_EXT2=y
+BR2_TARGET_ROOTFS_EXT2_4=y
 # BR2_TARGET_ROOTFS_TAR is not set
 
 # Bootloaders