turris: Use checkboard() instead of show_board_info()

Boards can use a sysinfo driver if a particular model name is needed.
Update this board to use checkboard() directly, rather than having a
weak function laid on top of a weak function.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/CZ.NIC/turris_mox/turris_mox.c b/board/CZ.NIC/turris_mox/turris_mox.c
index 63b8699..3489bdd 100644
--- a/board/CZ.NIC/turris_mox/turris_mox.c
+++ b/board/CZ.NIC/turris_mox/turris_mox.c
@@ -562,7 +562,7 @@
 	}
 }
 
-int show_board_info(void)
+int checkboard(void)
 {
 	int i, ret, board_version, ram_size, is_sd;
 	const char *pub_key, *model;