ARM: ux500: List DT compatibility using platform names rather than by board

So far, each ST-Ericsson board supported by Device Tree has been similar
enough to run though a single DT_MACHINE_INIT call. On the back of that
it has been suggested that we should reduce the number of compatible
strings in our dt_compat structure. After subsequent discussion with Arnd
Bergmann the conclusion was to list entries by platform as opposed to by
board.

The other suggestion was to use a single string which would cover all
supported platforms, but any wildcard entries would include unsupported
chipsets, such as the u5500 and potential new chips which no not yet have
DT functionality. Hence, the best solution which encompasses all supported
platforms, but no unsupported ones was to list the currently enabled four
chipsets; u8500, u8540, u9500 and u9540 instead.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>