PM / devfreq: events: add Exynos PPMU new events

Define new performance events supported by Exynos5422 SoC counters.
The counters are built-in in Dynamic Memory Controller and provide
information regarding memory utilization.

Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>