lib/built-in.o:(__modver+0x8): undefined reference to `__modver_version_show'
lib/built-in.o:(__modver+0x2c): undefined reference to `__modver_version_show'

Simplest to just not emit anything: if they've disabled SYSFS they probably
want the smallest kernel possible.
Reported-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>