arm64: defconfig: Enable squashfs support

squashfs can be a convenient way to use a root filesystem stored as a
file on some other root filesystem.
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/configs/defconfig

@@ -200,7 +200,7 @@ CONFIG_VFAT_FS=y
 CONFIG_TMPFS=y
 CONFIG_HUGETLBFS=y
 CONFIG_EFIVAR_FS=y
-# CONFIG_MISC_FILESYSTEMS is not set
+CONFIG_SQUASHFS=y
 CONFIG_NFS_FS=y
 CONFIG_NFS_V4=y
 CONFIG_ROOT_NFS=y