ARM: vexpress: Initial common clock support

This patch makes Versatile Express use the common clock framework
instead of the plat-versatile implementation.

It defines clock provider for VE's OSCs (clock generators) and
registers all required fixed and variable clock sources (for both
motherboard and core tile).

This is a simple conversion of the existing state and will be
extended (and migrated to drivers/clk) in the near future.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 17beb66..6374a08 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -310,14 +310,13 @@
 	select ARM_AMBA
 	select ARM_TIMER_SP804
 	select CLKDEV_LOOKUP
-	select HAVE_MACH_CLKDEV
+	select COMMON_CLK
 	select GENERIC_CLOCKEVENTS
 	select HAVE_CLK
 	select HAVE_PATA_PLATFORM
 	select ICST
 	select NO_IOPORT
 	select PLAT_VERSATILE
-	select PLAT_VERSATILE_CLOCK
 	select PLAT_VERSATILE_CLCD
 	help
 	  This enables support for the ARM Ltd Versatile Express boards.