drm/vkms: Fix use after frees on error paths

drm/vkms: Fix use after frees on error paths

These error paths free a pointer and then dereference it on the next line
to get the error code.  Save the error code first and then free the
memory.

Fixes: 3e4d5b30d2b2 ("drm/vkms: Allow to configure multiple CRTCs via configfs")
Fixes: 2f1734ba271b ("drm/vkms: Allow to configure multiple planes via configfs")
Fixes: 67d8cf92e13e ("drm/vkms: Allow to configure multiple encoders via configfs")
Fixes: 272acbca96a3 ("drm/vkms: Allow to configure multiple connectors via configfs")
Fixes: 13fc9b9745cc ("drm/vkms: Add and remove VKMS instances via configfs")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: José Expósito <jose.exposito89@gmail.com>
Link: https://lore.kernel.org/r/aPtfy2jCI_kb3Df7@stanley.mountain
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>