configs/{atngw100, atstk100x}: fix build of AVR32 defconfigs

Since we marked the AVR32 architecture deprecated, it can no longer be
selected in a normal configuration. This has caused the AVR32
defconfigs to fail to build in our daily Jenkins tests. In order to
make them build again, they must use BR2_DEPRECATED=y. Of course, when
we remove AVR32 completely, we'll remove those defconfigs as well.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>