Move the VC instance struct from omap_vdd_info into struct voltagedomain.
While moving, perform some misc. renames for readability.

No functional changes.

Summary of renames:
- rename omap_vc_instance to omap_vc_channel, since there is only
  one instance of the VC IP and this actually represents channels
  using TRM terminology.
- rename 'vc_common' field of VC channel which led to:
  s/vc->vc_common/vc->common/
- remove redundant '_data' suffix
- OMAP3: vc1 --> vc_mpu, vc2 --> vc_core
- omap_vc_bypass_scale_voltage() -> omap_vc_bypass_scale()
Signed-off-by: NKevin Hilman <khilman@ti.com>

merge

As part of the voltage layer cleanup, split out VC specific code into
a dedicated VC layer.  This patch primarily just moves VC code from
voltage.c into vc.c, and adds prototypes to vc.h.

No functional changes.

For readability, each function was given a local 'vc' pointer:

    struct omap_vc_instance_data *vc = voltdm->vdd->vc_data;

and a global replace of s/vdd->vc_data/vc/ was done.

Also vc_init was renamed to vc_init_channel to reflect that this is
per-VC channel initializtion.
Signed-off-by: NKevin Hilman <khilman@ti.com>