of: configfs: Fix compilation warning

of: configfs: Fix compilation warning

On 64-bit:
drivers/of/configfs.c: In function ‘cfs_overlay_item_dtbo_read’:
include/linux/kern_levels.h:5:18: warning: format ‘%u’ expects
argument of type ‘unsigned int’, but argument 4 has type
‘size_t {aka long unsigned int}’ [-Wformat=]

Signed-off-by: Nava kishore Manne <nava.manne@xilinx.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>