ARM: samsung: Limit SAMSUNG_PM_DEBUG config option to non-Exynos platforms

"Samsung PM Suspend debug" feature (controlled by SAMSUNG_PM_DEBUG
config option) is not working properly (debug messages are not
displayed after resume) on Exynos platforms because GPIOs restore
code is not implemented.

Add PLAT_S3C24XX, ARCH_S3C64XX and ARCH_S5PV210 dependencies to
SAMSUNG_PM_DEBUG config option to hide it on Exynos platforms.
Then convert Exynos code to not require <plat/pm-common.h>
header (use pr_debug() directly instead of S3C_PMDBG() macro and
remove redundant s3c_pm_*() calls).

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>