Linux 6.3 compat: idmapped mount API changes

Linux kernel 6.3 changed a bunch of APIs to use the dedicated idmap 
type for mounts (struct mnt_idmap), we need to detect these changes 
and make zfs work with the new APIs.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Youzhong Yang <yyang@mathworks.com>
Closes #14682

include/os/freebsd/spl/sys/types.h

@@ -105,7 +105,7 @@ typedef	u_longlong_t	len_t;
 
 typedef	longlong_t	diskaddr_t;
 
-typedef void		zuserns_t;
+typedef void		zidmap_t;
 
 #include <sys/debug.h>
 #endif	/* !_OPENSOLARIS_SYS_TYPES_H_ */