board: kontron: Remove <common.h> and add needed includes

Remove <common.h> from this board vendor directory and when needed
add missing include files directly.

Acked-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Acked-by: Michael Walle <michael@walle.cc>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/kontron/sl28/cmds.c b/board/kontron/sl28/cmds.c
index 08a22b5..7851361 100644
--- a/board/kontron/sl28/cmds.c
+++ b/board/kontron/sl28/cmds.c
@@ -5,10 +5,11 @@
  * Copyright (c) 2020 Kontron Europe GmbH
  */
 
-#include <common.h>
 #include <command.h>
 #include <i2c.h>
+#include <vsprintf.h>
 #include <linux/delay.h>
+#include <linux/errno.h>
 
 #define CPLD_I2C_ADDR 0x4a
 #define REG_UFM_CTRL 0x02