sysfs: sysfs_create_groups returns a value.

When I included the "empty" function for sysfs_create_groups() when
CONFIG_SYSFS=n, I forgot to return a value for it, so things blew up the
build.  This patch fixes that, stupid me.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>