misc: fastrpc: Fix an error handling path in fastrpc_rpmsg_probe()

If of_platform_populate() fails, some resources need to be freed as already
done in the other error handling paths.

Fixes: 278d56f9 ("misc: fastrpc: Reference count channel context")
Fixes: 3abe3ab3 ("misc: fastrpc: add secure domain support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/b909d2f3273b794ea0f1f78d14bc24affb08ea5f.1669398274.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>