Linux 6.8 compat: implement strlcpy fallback

Linux has removed strlcpy in favour of strscpy. This implements a
fallback implementation of strlcpy for this case.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #15805

module/os/linux/spl/spl-kmem-cache.c

@@ -28,6 +28,7 @@
 #include <sys/timer.h>
 #include <sys/vmem.h>
 #include <sys/wait.h>
+#include <sys/string.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/prefetch.h>