s390/dasd: fix string length handling

s390/dasd: fix string length handling

Building dasd_eckd.o with latest clang reveals this bug:

    CC      drivers/s390/block/dasd_eckd.o
      drivers/s390/block/dasd_eckd.c:1082:3: warning: 'snprintf' will always be truncated;
      specified size is 1, but format string expands to at least 11 [-Wfortify-source]
       1082 |                 snprintf(print_uid, sizeof(*print_uid),
            |                 ^
      drivers/s390/block/dasd_eckd.c:1087:3: warning: 'snprintf' will always be truncated;
      specified size is 1, but format string expands to at least 10 [-Wfortify-source]
       1087 |                 snprintf(print_uid, sizeof(*print_uid),
            |                 ^

Fix this by moving and using the existing UID_STRLEN for the arrays
that are being written to. Also rename UID_STRLEN to DASD_UID_STRLEN
to clarify its scope.

Fixes: 23596961b437 ("s390/dasd: split up dasd_eckd_read_conf")
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com> # build
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/1923
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20230828153142.2843753-2-hca@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>