drm/tinydrm/Kconfig: Remove menuconfig DRM_TINYDRM

This makes the tiny drivers visible by default without having to enable a
knob.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com> to it once
Link: https://patchwork.freedesktop.org/patch/msgid/20190725105132.22545-2-noralf@tronnes.org