[LOCAL] riscv: rzfive: defconfig: Update for renesas-drivers

Update the defconfig for Renesas RZ/Five systems:
  - Compile the kernel with warnings as errors,
  - Drop CONFIG_NFS_V4_1=y (removed in commit commit 7537db24806fdc3d
    ("NFS: Merge CONFIG_NFS_V4_1 with CONFIG_NFS_V4")).

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>