NFSD: Fix destination buffer size in nfsd4_ssc_setup_dul()

NFSD: Fix destination buffer size in nfsd4_ssc_setup_dul()

Commit 5304877936c0 ("NFSD: Fix strncpy() fortify warning") replaced
strncpy(,, sizeof(..)) with strlcpy(,, sizeof(..) - 1), but strlcpy()
already guaranteed NUL-termination of the destination buffer and
subtracting one byte potentially truncated the source string.

The incorrect size was then carried over in commit 72f78ae00a8e ("NFSD:
move from strlcpy with unused retval to strscpy") when switching from
strlcpy() to strscpy().

Fix this off-by-one error by using the full size of the destination
buffer again.

Cc: stable@vger.kernel.org
Fixes: 5304877936c0 ("NFSD: Fix strncpy() fortify warning")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>