powerpc/82xx/km: add testpin detection for mgcoge3ne

On mgcoge3ne we also want to start the test application if the testpin
is asserted. But we don't have a full POST test support yet. So simply
add a function to read the testpin value.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
diff --git a/board/keymile/common/common.h b/board/keymile/common/common.h
index dcfefc4..c74f569 100644
--- a/board/keymile/common/common.h
+++ b/board/keymile/common/common.h
@@ -134,6 +134,8 @@
 int fpga_reset(void);
 int toggle_eeprom_spi_bus(void);
 
+int get_testpin(void);
+
 int set_km_env(void);
 int fdt_set_node_and_value(void *blob,
 			char *nodename,