m68k/defconfig: Make NFS_V4 modular instead of builtin

This reduces the kernel image size by ca. 100 KiB, while still allowing
NFS root.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
diff --git a/arch/m68k/configs/mvme16x_defconfig b/arch/m68k/configs/mvme16x_defconfig
index e5e8262..d086acd 100644
--- a/arch/m68k/configs/mvme16x_defconfig
+++ b/arch/m68k/configs/mvme16x_defconfig
@@ -334,7 +334,7 @@
 CONFIG_SYSV_FS=m
 CONFIG_UFS_FS=m
 CONFIG_NFS_FS=y
-CONFIG_NFS_V4=y
+CONFIG_NFS_V4=m
 CONFIG_NFS_SWAP=y
 CONFIG_ROOT_NFS=y
 CONFIG_NFSD=m