kern-tools: fix conditional configuration items

kern-tools: fix conditional configuration items

Variables defined in .scc files have two purposes:

   - Documentation in the meta-series
   - Variables that can be tested in sub sections and other features

The second part of this functionality was broken when fixing configuration
for tiny/small systems. As a result, arch tests were failing and configs were
dropped.  This restores the existing functionality.

(From OE-Core rev: 4170e458e0f700319f4e1023c0c6c2d803449566)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>