ARM: EXYNOS: fix CPU1 hotplug on Exynos3250

CPU1 hotplug may hang when AFTR is used.  Fix it by:
- setting AUTOWAKEUP_EN bit in ARM_COREx_CONFIGURATION register in
  exynos_cpu_power_up()
- not clearing reserved bits of ARM_COREx_CONFIGURATION register in
  exynos_cpu_power_down()
- waiting while an undocumented register 0x0908 becomes non-zero in
  exynos_core_restart()
- using dsb_sev() instead of IPI in exynos_boot_secondary() on
  Exynos3250

This patch also fixes hotplug issues during resume from S2R:
$ echo mem > /sys/power/state
[  156.517266] Disabling non-boot CPUs ...
[  156.517781] IRQ18 no longer affine to CPU1
[  156.518043] CPU1: shutdown
[  156.544718] Enabling non-boot CPUs ...
[  156.554925] CPU1: Software reset
[  158.552631] CPU1: failed to come online
[  158.552753] Error taking CPU1 up: -5

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>