ARM: EXYNOS: Provide compatibility stubs for PM code in pm-core.h header

This patch adds several compatibility definitions that are not relevant
for Exynos, but are required by Samsung PM core.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>