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>

arch/arm/mach-tango/Kconfig

 config ARCH_TANGO
-	bool "Sigma Designs Tango4 (SMP87xx)" if ARCH_MULTI_V7
+	bool "Sigma Designs Tango4 (SMP87xx)"
+	depends on ARCH_MULTI_V7
 	# Cortex-A9 MPCore r3p0, PL310 r3p2
 	select ARCH_HAS_HOLES_MEMORYMODEL
 	select ARM_ERRATA_754322