net: tftp: Move tftp.h file from ./net to ./include/net

This change gives the ability to reuse the <tftp.h> header file by other
subsystems (like e.g. dfu).

Without this change compilation error emerges for the legacy update.c file.

Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

net/net.c

@@ -86,6 +86,7 @@
 #include <environment.h>
 #include <errno.h>
 #include <net.h>
+#include <net/tftp.h>
 #if defined(CONFIG_STATUS_LED)
 #include <miiphy.h>
 #include <status_led.h>
@@ -105,7 +106,6 @@
 #if defined(CONFIG_CMD_SNTP)
 #include "sntp.h"
 #endif
-#include "tftp.h"
 
 DECLARE_GLOBAL_DATA_PTR;