PM / devfreq: exynos-bus: Extract exynos_bus_profile_init()

This patch adds a new exynos_bus_profile_init() extracted
from exynos_bus_probe() for devfreq device using simple_ondemand governor
like parent devfreq device.

Signed-off-by: Artur Świgoń <a.swigon@samsung.com>
[cw00.choi: Edit description to indicate that new function is
for parent devfreq device]
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>