ARM: EXYNOS: Fix failed second suspend on Exynos4

On Exynos4412 boards (Trats2, Odroid U3) after enabling L2 cache in
56b60b8b ("ARM: 8265/1: dts: exynos4: Add nodes for L2 cache
controller") the second suspend to RAM failed. First suspend worked fine
but the next one hang just after powering down of secondary CPUs (system
consumed energy as it would be running but was not responsive).

The issue was caused by enabling delayed reset assertion for CPU0 just
after issuing power down of cores. This was introduced for Exynos4 in
13cfa6c4 ("ARM: EXYNOS: Fix CPU idle clock down after CPU off").

The whole behavior is not well documented but after checking with vendor
code this should be done like this (on Exynos4):
1. Enable delayed reset assertion when system is running (for all CPUs).
2. Disable delayed reset assertion before suspending the system.
   This can be done after powering off secondary CPUs.
3. Re-enable the delayed reset assertion when system is resumed.

Fixes: 13cfa6c4

 ("ARM: EXYNOS: Fix CPU idle clock down after CPU off")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>