drm: meson: rename module name to meson-drm

The module is currently named "meson.ko" which can lead to some
confusion, this patches renames it "meson-drm.ko"

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1486028864-19622-2-git-send-email-narmstrong@baylibre.com