Mediatek Genio 1200-EVK board has two MT6315 PMICs, powered by the
board system power rail (VSYS) and connected to the SPMI interface.
Add VSYS regulator node for system power rail and the supply inputs of
these two PMICs.
Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>