ARM: ux500: Move regulator-name properties out to board DTS files

Regulator supply names should be allocated by board rather than
per SoC, as the same SoC could be wired differently on varying
hardware. Here we push all regulator-name allocation out to the
dbx5x0 subordinate board files; HREF and Snowball.

Requested-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>