ARM: ux500: split the HREF DTS files from two to four

ARM: ux500: split the HREF DTS files from two to four

As the device tree conversion did away with the ability to
auto-detect the UIB (User Interface Board) version from attempting
to read an I2C address, we now have to pass the knowledge of
what UIB is mounted through the device tree. This gives rise
to four possible board permutations:

- HREF prior to v60, ST UIB (hrefprev60-stuib)
- HREF prior to v60, TVK1281618 UIB (hrefprev60-tvk)
- HREF v60 and later, ST UIB (href60plus-stuib)
- HREF v60 and later, TVK1281618 UIB (hrefv60plus-tvk)

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>