AMD and GFXUMA: move setup_uma_memory() to northbridge

UMA region can be determined at any time after the amount
of RAM is known and before the uma_resource() call.

Change-Id: I2a0bf2d3cad55ee70e889c88846f962b7faa0c7e
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/1379
Reviewed-by: Zheng Bao <zheng.bao@amd.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Anton Kochkov <anton.kochkov@gmail.com>

src/include/device/device.h

@@ -112,7 +112,6 @@ extern struct resource	*free_resources;
 extern struct bus	*free_links;
 
 /* IGD UMA memory */
-void setup_uma_memory(void);
 extern uint64_t uma_memory_base;
 extern uint64_t uma_memory_size;