net: tftp: Fix load_block offset calculation

When load the last block, the "len" might not be a block size. This cause
loading the incorrect last block data.

The fix change "len" to tftp_block_size and minus one tftp_block_size
for offset calculation.

Use same offset calculation formula as in store_block().
Signed-off-by: NLey Foon Tan <ley.foon.tan@intel.com>
Reviewed-By: NRamon Fried <rfried.dev@gmail.com>

net/tftp.c

@@ -234,7 +234,8 @@ static void new_transfer(void)
 static int load_block(unsigned block, uchar *dst, unsigned len)
 {
 	/* We may want to get the final block from the previous set */
-	ulong offset = ((int)block - 1) * len + tftp_block_wrap_offset;
+	ulong offset = block * tftp_block_size + tftp_block_wrap_offset -
+		       tftp_block_size;
 	ulong tosend = len;
 
 	tosend = min(net_boot_file_size - offset, tosend);