ARM: EXYNOS: Use platform device name as power domain name

The power domain nodes in DTS may be very generic (e.g. "power-domain"
for Exynos 5420) making it very hard to debug:

$ cat /sys/kernel/debug/pm_genpd/pm_genpd_summary
    domain                      status         slaves
power-domain                    on

Use platform device name instead so the names will be a little more
user friendly:
    domain                      status         slaves
100440e0.power-domain           on
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Suggested-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Suggested-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: NChanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: NKevin Hilman <khilman@linaro.org>
Signed-off-by: NKukjin Kim <kgene@kernel.org>

arch/arm/mach-exynos/pm_domains.c

@@ -135,7 +135,7 @@ static __init int exynos4_pm_init_power_domain(void)
 			return -ENOMEM;
 		}
 
-		pd->pd.name = kstrdup(np->name, GFP_KERNEL);
+		pd->pd.name = kstrdup(dev_name(dev), GFP_KERNEL);
 		pd->name = pd->pd.name;
 		pd->base = of_iomap(np, 0);
 		pd->pd.power_off = exynos_pd_power_off;