The various devm_ functions allocate memory that is released when a driver
detaches. This patch replaces the use of kzalloc by devm_kzalloc.

Additionally, this patch fixes a memory leak: some memory was allocated for
'panel' but not released when the subsequent call to setup_vsync fails.
Signed-off-by: Damien Cassou <damien.cassou@lifl.fr>
Acked-by: David Brown <davidb@codeaurora.org>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>