dt-bindings: mfd: spacemit,p1: Add individual regulator supply properties

dt-bindings: mfd: spacemit,p1: Add individual regulator supply properties

Add supply properties that match the P1 PMIC's actual hardware topology
where each buck converter has its own VIN pin and LDO groups share
common input pins. Supply names are defined according to the pinout
names in the P1 datasheet.

The existing "vin-supply" is dropped from the binding document as the
updated spacemit P1 driver no longer parses it. Only the per-rail names
("vin1-supply", "vin2-supply", ...) are supported.

Signed-off-by: Guodong Xu <guodong@riscstar.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Alex Elder <elder@riscstar.com>
Link: https://patch.msgid.link/20260206-spacemit-p1-v4-1-8f695d93811e@riscstar.com
Signed-off-by: Lee Jones <lee@kernel.org>