boost: fix build failures after version bump

Fix build failures that happened after the version bump such as:
http://autobuild.buildroot.net/results/570/570b091702763b29843d9207bc14dea67085fea0/
http://autobuild.buildroot.net/results/c26/c26498f1a4e6bcbc3a2dfce6a51fa7d21b72f21f/


and other failures by disabling the new (1.54+) coroutine and log
libraries which weren't handled and hence enabled by default.

These also made the target size bigger and build times longer
unnecessarily.

When/if they are needed for some future user this can be revisited and
their proper conditions for enablement assesed.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Acked-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>