ARM: s3c64xx: prepare initcalls for multiplatform

In a multiplatform kernel, each initcall is run regardless
of the platform it is meant for, so it must not attempt to
access SoC-specific registers.

This adds 'if (soc_is_s3c64xx)' to all initcalls that are
specific to the s3c64xx platform, to prevent them from breaking
other platforms once we can build them into a combined kernel.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>