Cocinnele reports a warning

WARNING: Suspicious code. resource_size is maybe missing with root

The root cause is the function resource_size is not used when needed

Use resource_size() on variable "root" of type resource
Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>