ARM: stm32: use "depends on" instead of "if" after prompt

This appeared after the global fixups by commit e3246542 ("ARM: use
"depends on" for SoC configs instead of "if" after prompt"). Fix it now.

Link: https://lore.kernel.org/r/20190710051320.8738-1-yamada.masahiro@socionext.com


Fixes: e3246542 ("ARM: use "depends on" for SoC configs instead of "if" after prompt")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>