net: lwip: tftp: add support for setting blocksize at runtime

Add support for setting the blocksize at runtime via the tftpblocksize env
variable as such is done with the legacy stack (CONFIG_NET).

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
diff --git a/net/lwip/tftp.c b/net/lwip/tftp.c
index 2791452..94bacf6 100644
--- a/net/lwip/tftp.c
+++ b/net/lwip/tftp.c
@@ -157,8 +157,10 @@
 static int tftp_loop(struct udevice *udev, ulong addr, char *fname,
 		     ip_addr_t srvip, uint16_t srvport)
 {
+	int blksize = CONFIG_TFTP_BLOCKSIZE;
 	struct netif *netif;
 	struct tftp_ctx ctx;
+	const char *ep;
 	err_t err;
 
 	if (!fname || addr == 0)
@@ -187,7 +189,10 @@
 	if (!(err == ERR_OK || err == ERR_USE))
 		log_err("tftp_init_client err: %d\n", err);
 
-	tftp_client_set_blksize(CONFIG_TFTP_BLOCKSIZE);
+	ep = env_get("tftpblocksize");
+	if (ep)
+		blksize = simple_strtol(ep, NULL, 10);
+	tftp_client_set_blksize(blksize);
 
 	ctx.start_time = get_timer(0);
 	err = tftp_get(&ctx, &srvip, srvport, fname, TFTP_MODE_OCTET);