Fix gcc11 compiler issue "-Werror=stringop-overflow="

Fix gcc11 compiler issue "-Werror=stringop-overflow="

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14699

[3548/3991] Compiling source3/winbindd/winbindd_pam.c
../../source3/winbindd/winbindd_pam.c: In function ‘winbindd_dual_pam_auth_cached’:
../../source3/winbindd/winbindd_pam.c:1069:18: error: ‘winbindd_get_creds’ accessing 128 bytes in a region of size 8 [-Werror=stringop-overflow=]
 1069 |         result = winbindd_get_creds(domain,
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~
 1070 |                                     state->mem_ctx,
      |                                     ~~~~~~~~~~~~~~~
 1071 |                                     &sid,
      |                                     ~~~~~
 1072 |                                     &my_info3,
      |                                     ~~~~~~~~~~
 1073 |                                     &cached_nt_pass,
      |                                     ~~~~~~~~~~~~~~~~
 1074 |                                     &cached_salt);
      |                                     ~~~~~~~~~~~~~
../../source3/winbindd/winbindd_pam.c:1069:18: note: referencing argument 5 of type ‘const uint8_t **’ {aka ‘const unsigned char **’}
../../source3/winbindd/winbindd_pam.c:1069:18: error: ‘winbindd_get_creds’ accessing 128 bytes in a region of size 8 [-Werror=stringop-overflow=]
../../source3/winbindd/winbindd_pam.c:1069:18: note: referencing argument 6 of type ‘const uint8_t **’ {aka ‘const unsigned char **’}
In file included from ../../source3/winbindd/winbindd.h:359,
                 from ../../source3/winbindd/winbindd_pam.c:26:
../../source3/winbindd/winbindd_proto.h:251:10: note: in a call to function ‘winbindd_get_creds’
  251 | NTSTATUS winbindd_get_creds(struct winbindd_domain *domain,
      |          ^~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Guenther

Signed-off-by: Guenther Deschner <gd@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>