net: tftp: Fix store_block offset calculation

tftp_cur_block start with 1 for first block, but tftp_cur_block counter is
start with zero when block number is rollover. The existing code
"tftp_cur_block - 1" will cause the block number become -1 in store_block()
when tftp_cur_block is 0 when tftp_cur_block is rollover.

The fix pass in tftp_cur_block to store_block() and minus the
tftp_block_size when do the offset calculation.
Signed-off-by: NLey Foon Tan <ley.foon.tan@intel.com>
Reviewed-By: NRamon Fried <rfried.dev@gmail.com>

net/tftp.c

@@ -159,7 +159,8 @@ static unsigned short tftp_window_size_option = TFTP_WINDOWSIZE;
 
 static inline int store_block(int block, uchar *src, unsigned int len)
 {
-	ulong offset = block * tftp_block_size + tftp_block_wrap_offset;
+	ulong offset = block * tftp_block_size + tftp_block_wrap_offset -
+			tftp_block_size;
 	ulong newsize = offset + len;
 	ulong store_addr = tftp_load_addr + offset;
 #ifdef CONFIG_SYS_DIRECT_FLASH_TFTP
@@ -652,7 +653,7 @@ static void tftp_handler(uchar *pkt, unsigned dest, struct in_addr sip,
 		timeout_count_max = tftp_timeout_count_max;
 		net_set_timeout_handler(timeout_ms, tftp_timeout_handler);
 
-		if (store_block(tftp_cur_block - 1, pkt + 2, len)) {
+		if (store_block(tftp_cur_block, pkt + 2, len)) {
 			eth_halt();
 			net_set_state(NETLOOP_FAIL);
 			break;