ARM: enable ARM_HAS_SG_CHAIN for multiplatform

Enable ARM_HAS_SG_CHAIN for all multiplatform targets, it makes sense
to enable on all "modern" platforms; downsides are limited for platforms
that don't need it.
Requested-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NOlof Johansson <olof@lixom.net>

arch/arm/Kconfig

@@ -307,6 +307,7 @@ config ARCH_MULTIPLATFORM
 	bool "Allow multiple platforms to be selected"
 	depends on MMU
 	select ARCH_WANT_OPTIONAL_GPIOLIB
+	select ARM_HAS_SG_CHAIN
 	select ARM_PATCH_PHYS_VIRT
 	select AUTO_ZRELADDR
 	select COMMON_CLK