drm: DRM_WERROR should depend on DRM

There is no point in asking the user about enforcing the DRM compiler
warning policy when configuring a kernel without DRM support.

Fixes: f89632a9 ("drm: Add CONFIG_DRM_WERROR")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/631a1f4c066181b54617bfe2f38b0bd0ac865b68.1711474200.git.geert+renesas@glider.be


Signed-off-by: Jani Nikula <jani.nikula@intel.com>