This patch converts exynos4_bus driver to use common PPMU code
(exynos_ppmu.c) instead of individual functions related to PPC
because PPMU is integrated module with both PPC and Bus event
generator. When using PPMU to get bus performance read/write
event exynos4_bus driver deson't need to consider memory type.

Signed-off-by: Chanwoo Choi
[bzolnier: splitted out changes from the bigger patch]
Signed-off-by: Bartlomiej Zolnierkiewicz
Signed-off-by: MyungJoo Ham