ARM: tegra: clock: Moved common bus capping code

Moved common shared bus capping code into a separate file (currently
bus capping is supported on Tegra3 only).

Bug 1186037

Change-Id: Ie35c74cf9b4db65beacb9408942efb632c845193
Signed-off-by: Alex Frid <afrid@nvidia.com>
Reviewed-on: http://git-master/r/196730
Reviewed-by: Mandar Padmawar <mpadmawar@nvidia.com>
Tested-by: Mandar Padmawar <mpadmawar@nvidia.com>

Conflicts:
	arch/arm/mach-tegra/dvfs.h
	arch/arm/mach-tegra/tegra3_dvfs.c