drm/omap: fix spelling mistake "propert" -> "property"

There is a spelling mistake in a pr_err message. Fix it.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200805102015.14891-1-colin.king@canonical.com