arm,arm64,drivers: move externs in a new header file

Create a new header file (include/linux/arch_topology.h) and put there
declarations of interfaces used by arm, arm64 and drivers code.

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index acf9937..76c19aa 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -13,6 +13,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/arch_topology.h>
 #include <linux/cpu.h>
 #include <linux/cpufreq.h>
 #include <linux/device.h>