ARM: s3c64xx: mark regulator init data as unused

The smdk6410 board defines lots of regulator settings, but uses
most of them only in certain configurations, and otherwise leaves
them without any references, so we get lots of randconfig warnings
about them:

mach-s3c64xx/mach-smdk6410.c:303:35: error: 'smdk6410_vddarm' defined but not used [-Werror=unused-variable]
mach-s3c64xx/mach-smdk6410.c:316:35: error: 'smdk6410_vddint' defined but not used [-Werror=unused-variable]
mach-s3c64xx/mach-smdk6410.c:327:35: error: 'smdk6410_vddhi' defined but not used [-Werror=unused-variable]
mach-s3c64xx/mach-smdk6410.c:335:35: error: 'smdk6410_vddpll' defined but not used [-Werror=unused-variable]
mach-s3c64xx/mach-smdk6410.c:343:35: error: 'smdk6410_vdduh_mmc' defined but not used [-Werror=unused-variable]

This marks all regulator_init_data structures in this file as
__maybe_unused, indicating that we don't care whether there
are any references or not in a given configuration.

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