drm: Drop commas after SoC match table sentinels

It does not make sense to have a comma after a sentinel, as any new
elements must be added before the sentinel.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/298f0644275d7d0b4aa3ee7143756a2431a4900c.1646311443.git.geert+renesas@glider.be