drm: bridge: it66121: fix a resource leak in probe

In the original code if the "ctx = devm_kzalloc()" allocation failed
then we should have called of_node_put(ep); before returning.  It's
actually a bit easier to do the allocation first before assigning
ep = of_graph_get_endpoint_by_regs().

Fixes: 988156dc

 ("drm: bridge: add it66121 driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/YJ+ZgXTFa6voZuJG@mwanda