common: Always include errno.h in common.h

We want people using errnos for errors instead of -1, so make it easy
by always including the definition of all the errnos.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/common.h

@@ -16,6 +16,7 @@ typedef volatile unsigned short vu_short;
 typedef volatile unsigned char	vu_char;
 
 #include <config.h>
+#include <errno.h>
 #include <asm-offsets.h>
 #include <linux/bitops.h>
 #include <linux/types.h>