OMAP2+: voltage: start towards a new voltagedomain layer

Start cleaning up the voltage layer to have a voltage domain layer
that resembles the structure of the existing clock and power domain
layers.  To that end:

- move the 'struct voltagedomain' out of 'struct omap_vdd_info' to
  become the primary data structure.

- convert any functions taking a pointer to struct omap_vdd_info into
  functions taking a struct voltagedomain pointer.

- convert the register & initialize of voltage domains to look like
  that of powerdomains

- convert omap_voltage_domain_lookup() to voltdm_lookup(), modeled
  after the current powerdomain and clockdomain lookup functions.

- omap_voltage_late_init(): only configure VDD info when
  the vdd_info struct is non-NULL

Signed-off-by: Kevin Hilman <khilman@ti.com>

arch/arm/mach-omap2/sr_device.c

@@ -102,7 +102,7 @@ static int sr_dev_init(struct omap_hwmod *oh, void *user)
 	sr_data->senn_mod = 0x1;
 	sr_data->senp_mod = 0x1;
 
-	sr_data->voltdm = omap_voltage_domain_lookup(oh->vdd_name);
+	sr_data->voltdm = voltdm_lookup(oh->vdd_name);
 	if (IS_ERR(sr_data->voltdm)) {
 		pr_err("%s: Unable to get voltage domain pointer for VDD %s\n",
 			__func__, oh->vdd_name);