Bluetooth: L2CAP: Fix build errors in some archs

jira VULN-155016
cve-pre CVE-2023-53305
commit-author Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
commit fc5ae5b

This attempts to fix the follow errors:

In function 'memcmp',
    inlined from 'bacmp' at ./include/net/bluetooth/bluetooth.h:347:9,
    inlined from 'l2cap_global_chan_by_psm' at
    net/bluetooth/l2cap_core.c:2003:15:
./include/linux/fortify-string.h:44:33: error: '__builtin_memcmp'
specified bound 6 exceeds source size 0 [-Werror=stringop-overread]
   44 | #define __underlying_memcmp     __builtin_memcmp
      |                                 ^
./include/linux/fortify-string.h:420:16: note: in expansion of macro
'__underlying_memcmp'
  420 |         return __underlying_memcmp(p, q, size);
      |                ^~~~~~~~~~~~~~~~~~~
In function 'memcmp',
    inlined from 'bacmp' at ./include/net/bluetooth/bluetooth.h:347:9,
    inlined from 'l2cap_global_chan_by_psm' at
    net/bluetooth/l2cap_core.c:2004:15:
./include/linux/fortify-string.h:44:33: error: '__builtin_memcmp'
specified bound 6 exceeds source size 0 [-Werror=stringop-overread]
   44 | #define __underlying_memcmp     __builtin_memcmp
      |                                 ^
./include/linux/fortify-string.h:420:16: note: in expansion of macro
'__underlying_memcmp'
  420 |         return __underlying_memcmp(p, q, size);
      |                ^~~~~~~~~~~~~~~~~~~

Fixes: 332f179 ("Bluetooth: L2CAP: Fix l2cap_global_chan_by_psm regression")
	Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
(cherry picked from commit fc5ae5b)
	Signed-off-by: Roxana Nicolescu <rnicolescu@ciq.com>

Author: roxanan1996

net/bluetooth/l2cap_core.c

@@ -1991,11 +1991,11 @@ static struct l2cap_chan *l2cap_global_chan_by_psm(int state, __le16 psm,
 			src_match = !bacmp(&c->src, src);
 			dst_match = !bacmp(&c->dst, dst);
 			if (src_match && dst_match) {
-				c = l2cap_chan_hold_unless_zero(c);
-				if (c) {
-					read_unlock(&chan_list_lock);
-					return c;
-				}
+				if (!l2cap_chan_hold_unless_zero(c))
+					continue;
+
+				read_unlock(&chan_list_lock);
+				return c;
 			}
 
 			/* Closest match */