kconfig: replace 'oldnoconfig' with 'olddefconfig', and keep the old name as an alias

As 67d34a6a said, 'oldnoconfig' doesn't
set new symbols to 'n', but instead sets it to their default values.

So, this patch replaces 'oldnoconfig' with 'olddefconfig', stop making
people confused, and keep the old name 'oldnoconfig' as an alias,
because people already are dependent on its behavior with the
counter-intuitive name.

Signed-off-by: Adam Lee <adam8157@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>