ARM: S5PV310: Optimize interrupt source searching code
ARM: S5PV310: Optimize interrupt source searching code

It is reported by Junseok Jung that using clz instruction is
better instead of using for-loop to find the interrupt source.
This patch modifies interrupt source searching code using __ffs().
The __ffs() is implemented using clz instruction.

Suggested-by: Junseok Jung <0b7ee67edaa6a762d4d10f57f32e1d397f1c37c5@samsung.com>
Signed-off-by: Changhwan Youn <d2790e43565480f594576f44f7b01681db7143f2@samsung.com>
Signed-off-by: Kukjin Kim <3fc711f4e08bc570a586748633ff7c76d0e1e253@samsung.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs