populate_sdk_ext: do not require CONF_VERSION (e.g. local.conf version) to be set

populate_sdk_ext: do not require CONF_VERSION (e.g. local.conf version) to be set

The version checks for local.conf/site.conf/bblayers.conf are all optional,
and aren't enforced (by insane class) if the versions aren't set.

As bitbake-setup writes out a blank local.conf, it doesn't put a version in it
either. Also, esdk bundle has a fixed set of layers and is not at risk of
needing to update its own local.conf.

The same condition is already in place for esdk's bblayers.conf for similar reasons.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>