regulator: dt-bindings: mt6360: add buck regulator supplies

regulator: dt-bindings: mt6360: add buck regulator supplies

MT6360 PMIC provides 2 buck and 6 ldo regulators, that have each one a
separate supply.
Currently, the supplies for the ldo regulators are described in the
dt-bindings but the ones for the buck regulators are not.

Add the descriptions for these missing supplies.

Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
Link: https://patch.msgid.link/20260414-mtk-g1200-pmic-cleanup-v1-1-2a7193ed4e93@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>