amba: Add Kconfig file

Rather than duplicate the ARM_AMBA Kconfig symbol in both 32-bit and
64-bit ARM architectures, move the common definition to drivers/amba
where dependent drivers will be located.

Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/Kconfig

@@ -1259,9 +1259,6 @@ source "arch/arm/common/Kconfig"
 
 menu "Bus support"
 
-config ARM_AMBA
-	bool
-
 config ISA
 	bool
 	help

arch/arm64/Kconfig

@@ -166,9 +166,6 @@ endmenu
 
 menu "Bus support"
 
-config ARM_AMBA
-	bool
-
 config PCI
 	bool "PCI support"
 	help

drivers/amba/Kconfig

@@ -0,0 +1,2 @@
+config ARM_AMBA
+	bool