powerpc: wii_defconfig: Enable OTP by default

This selects the nintendo-otp module when building for this platform.

Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210801073822.12452-6-linkmauve@linkmauve.fr