sysfs, kernfs: drop unused params from sysfs_fill_super()

sysfs_fill_super() takes three params - @sb, @data and @silent - but
uses only @sb.  Drop the latter two.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>