openrisc: remove undefined of_get_cpu_node declaration

This patch removes the declaration of the function 'of_get_cpu_node'
which is not defined for openrisc. This is in preparation to move
it's definition from PPC to DT common code.

Again it could be there as it was originally copied from powerpc.
Acked-by: NJonas Bonn <jonas@southpole.se>
Signed-off-by: NSudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>

arch/openrisc/include/asm/prom.h

@@ -44,9 +44,6 @@ void of_parse_dma_window(struct device_node *dn, const void *dma_window_prop,
 
 extern void kdump_move_device_tree(void);
 
-/* CPU OF node matching */
-struct device_node *of_get_cpu_node(int cpu, unsigned int *thread);
-
 /* Get the MAC address */
 extern const void *of_get_mac_address(struct device_node *np);