ARM: dts: omap5-uevm: document regulator signals used on the actual board

ARM: dts: omap5-uevm: document regulator signals used on the actual board

commit 7e59547a9d2d9bfc689f7e2a2d4eaaa8593dea68
(ARM: dts: OMAP5: Add Palmas MFD node and regulator nodes)
introduced regulator entries for OMAP5uEVM.

However, currently we use the Palmas regulator names which is used for
different purposes on uEVM. Document the same based on 750-2628-XXX
boards - which is meant to be supported by this dts.

Reported-by: Marc Jüttner <m-juettner@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: J Keerthy <j-keerthy@ti.com>
Acked-by: Benoit Cousson <benoit.cousson@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>