arm/dts: k3-j7200-r5-common: Hook buck1_reg to vtm supply

Hook buck1_reg to vtm avs supply.

Signed-off-by: Gowtham Tammana <g-tammana@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210714205300.17424-5-g-tammana@ti.com