ARM: tango: use "depends on" instead of "if" after prompt

This platform was recently added, so missed the global fixup by
commit e3246542

 ("ARM: use "depends on" for SoC configs instead
of "if" after prompt").  Fix it now.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Signed-off-by: Olof Johansson <olof@lixom.net>