arm64: dts: ti: k3-am68-sk: Fix regulator hierarchy

arm64: dts: ti: k3-am68-sk: Fix regulator hierarchy

Update the vin-supply of the TLV71033 regulator from LM5141 (vsys_3v3)
to LM61460 (vsys_5v0) to match the schematics. Add a fixed regulator
node for the LM61460 5V supply to support this change.

AM68-SK schematics: https://www.ti.com/lit/zip/sprr463

Fixes: a266c180b398 ("arm64: dts: ti: k3-am68-sk: Add support for AM68 SK base board")
Cc: stable@vger.kernel.org
Signed-off-by: Yemike Abhilash Chandra <y-abhilashchandra@ti.com>
Reviewed-by: Neha Malcom Francis <n-francis@ti.com>
Reviewed-by: Udit Kumar <u-kumar1@ti.com>
Link: https://lore.kernel.org/r/20250415111328.3847502-3-y-abhilashchandra@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>