media: pci: mgb4: include linux/errno.h

The errno.h header is not always included indirectly, leading
to rare randconfig build warnings.

drivers/media/pci/mgb4/mgb4_regs.c:20:11: error: use of undeclared identifier 'EINVAL'
   20 |                 return -EINVAL;

Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Hans Verkuil <[email protected]>

Author: arndb

drivers/media/pci/mgb4/mgb4_regs.c

@@ -5,6 +5,7 @@
  */
 
 #include <linux/ioport.h>
+#include <linux/errno.h>
 #include "mgb4_regs.h"
 
 int mgb4_regs_map(struct resource *res, struct mgb4_regs *regs)