sysfs: remove unused include of kernfs-internal.h

This include is not needed (fs/sysfs/file.c builds just fine without
it). Remove it.

Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>