vfio/ccw: replace one-element array with flexible-array member

One-element arrays are deprecated, and we are replacing them with flexible
array members instead. So, replace one-element array with flexible-array
member in struct vfio_ccw_parent and refactor the rest of the code
accordingly.

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/297Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/3c10549ebe1564eade68a2515bde233527376971.1684805398.git.gustavoars@kernel.orgSigned-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

drivers/s390/cio/vfio_ccw_drv.c

@@ -171,7 +171,8 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
 		return -ENODEV;
 	}
 
-	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
+	parent = kzalloc(sizeof(*parent) + sizeof(struct mdev_type *),
+			 GFP_KERNEL);
 	if (!parent)
 		return -ENOMEM;
 

drivers/s390/cio/vfio_ccw_private.h

@@ -79,7 +79,7 @@ struct vfio_ccw_parent {
 
 	struct mdev_parent	parent;
 	struct mdev_type	mdev_type;
-	struct mdev_type	*mdev_types[1];
+	struct mdev_type	*mdev_types[];
 };
 
 /**