highbank: switch to use the Arm SP804 DM_TIMER driver

So far the Calxeda machines were using the CONFIG_SYS_TIMER_* macros to
simply hardcode the address of the counter register of the SP804 timer.
This method is deprecated and scheduled for removal.

Use the newly introduced SP804 DM_TIMER driver to provide timer
functionality on Highbank and Midway machines. The base address and base
frequency are taken from the devicetree.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 710f171..453bef9 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -769,6 +769,8 @@
 	select AHCI
 	select DM_ETH
 	select PHYS_64BIT
+	select TIMER
+	select SP804_TIMER
 	imply OF_HAS_PRIOR_STAGE
 
 config ARCH_INTEGRATOR