common: Drop log.h from common header

Move this header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/net/dns.c b/net/dns.c
index 67d761d..e35c4dc 100644
--- a/net/dns.c
+++ b/net/dns.c
@@ -25,6 +25,7 @@
 #include <common.h>
 #include <command.h>
 #include <env.h>
+#include <log.h>
 #include <net.h>
 #include <asm/unaligned.h>