mx6: soc: Update the comments of set_ldo_voltage()

Commit 3d622b78 (mx6: soc: Introduce set_ldo_voltage()) introduces
set_ldo_voltage() function that can be used to set the voltages
of any of the three LDO regulators controlled by the PMU_REG_CORE register.

Prior to this commit there was a single set_vddsoc() which only configured the
VDDSOC regulator.

Update the comments to align with the new set_ldo_voltage() implementation.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>

arch/arm/cpu/armv7/mx6/soc.c

@@ -124,10 +124,9 @@ static void clear_ldo_ramp(void)
 }
 
 /*
- * Set the VDDSOC
+ * Set the PMU_REG_CORE register
  *
- * Mask out the REG_CORE[22:18] bits (REG2_TRIG) and set
- * them to the specified millivolt level.
+ * Set LDO_SOC/PU/ARM regulators to the specified millivolt level.
  * Possible values are from 0.725V to 1.450V in steps of
  * 0.025V (25mV).
  */