linux-yocto: Handle /bin/awk issues

Standardise on /usr/bin/awk, else kernel-devsrc depends on /bin/awk which
the system doesn't provide and core-image-sato-sdk (which depends on
kernel-devsrc) will fail to build.

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