ARM: versatile: switch to DT only booting and remove legacy code

With DT support for clocks, irqchips, timers, and PCI now in place, DT
based booting has feature parity with non-DT legacy boot. The final
piece is actually enabling common clock support on Versatile. Enabling
full DT support requires either removing the old Versatile clock code,
updating the legacy boot to use the common clock code, or making DT and
legacy boot mutually exclusive. Given that removing legacy boot code is
the goal anyway, I am going with the 1st option.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>