arm: uniphier: use DM_TIMER of arm a9 global timer

All uniphier v7 SoCs have cortex-a9 and use cortex-a9 global timer
in a simple implementation. Now DM_TIMER of it is available
on 35751c7f3f ("timer: sti: convert sti-timer to arm a9 global timer"),
so let's switch to it.

The old driver reads the lower 32bits of counter field
and sets the prescaler as 50 with PERIPHCLK(=50MHz),
so the global timer works as a 32-bit 1MHz timer.

The DM_TIMER uses the whole 64bits with no prescaler,
so the global timer works as a 64-bit PERIPHCLK timer.

CONFIG_SYS_HZ_CLOCK is set as the default PERIPHCLK frequency,
if there is no 'clocks' property in devicetree.

Signed-off-by: Dai Okamura <okamura.dai@socionext.com>
diff --git a/arch/arm/mach-uniphier/Kconfig b/arch/arm/mach-uniphier/Kconfig
index 3a8eee7..c570fb3 100644
--- a/arch/arm/mach-uniphier/Kconfig
+++ b/arch/arm/mach-uniphier/Kconfig
@@ -12,6 +12,7 @@
 	select ARMV7_NONSEC
 	select CPU_V7A
 	select CPU_V7_HAS_NONSEC
+	select ARM_GLOBAL_TIMER if TIMER
 
 config ARCH_UNIPHIER_V8_MULTI
 	bool "UniPhier V8 SoCs"