kernel: use olddefconfig as the primary target for KERNEL_CONFIG_COMMAND

kernel: use olddefconfig as the primary target for KERNEL_CONFIG_COMMAND

As was warned by commit 312ee68752fa [kconfig: announce removal of
oldnoconfig if used], oldnoconfig has been removed from the 4.20 kernel.

So we switch our default mode to olddefconfig.

commit fb16d8912 [kconfig: replace 'oldnoconfig' with 'olddefconfig',
and keep the old name as an alias] introduced olddefconfig in the 3.10
kernel, we shuffle oldnoconfig to the fallback target.

The fallback mode allows kernels between 3.10 and the currently listed
oldest kernel of 3.2 to continue to configure.

(From OE-Core rev: 8593dcb7e8c938530ff00ffedf7f3d02d26c3bad)

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