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/tftp.c b/net/tftp.c
index 3348521..180140e 100644
--- a/net/tftp.c
+++ b/net/tftp.c
@@ -12,6 +12,7 @@
 #include <env.h>
 #include <image.h>
 #include <lmb.h>
+#include <log.h>
 #include <mapmem.h>
 #include <net.h>
 #include <net/tftp.h>