moveconfig: Ignore duplicate configs when moving

When moving configs, it is important to know what was defined in the
config header even if it duplicates the configs coming from Kconfig.

This is specifically needed for the case where a config is set to
default 'y' in the Kconfig. This would previously cause the actual value
from the include config to be filtered out, and moveconfig.py would
think that it was 'n'... This means that the value that should be 'y'
is now (in every defconfig) set to 'not set'.

tools/moveconfig.py now defines KCONFIG_IGNORE_DUPLICATES to prevent the
filtering from happening and selecting wrong values for the defconfig.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>