smb: client: fix possible double free in smb2_set_ea()

Clang static checker(scan-build) warning：
fs/smb/client/smb2ops.c:1304:2: Attempt to free released memory.
 1304 |         kfree(ea);
      |         ^~~~~~~~~

There is a double free in such case:
'ea is initialized to NULL' -> 'first successful memory allocation for
ea' -> 'something failed, goto sea_exit' -> 'first memory release for ea'
-> 'goto replay_again' -> 'second goto sea_exit before allocate memory
for ea' -> 'second memory release for ea resulted in double free'.

Re-initialie 'ea' to NULL near to the replay_again label, it can fix this
double free problem.

Fixes: 4f1fffa ("cifs: commands that are retried should have replay flag set")
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Su Hui <suhui@nfschina.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/smb2ops.c

@@ -1158,7 +1158,7 @@ smb2_set_ea(const unsigned int xid, struct cifs_tcon *tcon,
 	struct cifs_fid fid;
 	unsigned int size[1];
 	void *data[1];
-	struct smb2_file_full_ea_info *ea = NULL;
+	struct smb2_file_full_ea_info *ea;
 	struct smb2_query_info_rsp *rsp;
 	int rc, used_len = 0;
 	int retries = 0, cur_sleep = 1;
@@ -1179,6 +1179,7 @@ smb2_set_ea(const unsigned int xid, struct cifs_tcon *tcon,
 	if (!utf16_path)
 		return -ENOMEM;
 
+	ea = NULL;
 	resp_buftype[0] = resp_buftype[1] = resp_buftype[2] = CIFS_NO_BUFFER;
 	vars = kzalloc(sizeof(*vars), GFP_KERNEL);
 	if (!vars) {