riscv: defconfig: enable DRM_NOUVEAU

riscv: defconfig: enable DRM_NOUVEAU

[ Upstream commit ffa7a9141bb70702744a312f904b190ca064bdd7 ]

Both RADEON and NOUVEAU graphics cards are supported on RISC-V. Enabling
the one and not the other does not make sense.

As typically at most one of RADEON, NOUVEAU, or VIRTIO GPU support will be
needed DRM drivers should be compiled as modules.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>