Make 1-bit bitfields unsigned

This fixes -Wsingle-bit-bitfield-constant-conversion warning from
clang-16 like:

lib/libzfs/libzfs_dataset.c:4529:19: error: implicit truncation
  from 'int' to a one-bit wide bit-field changes value from
  1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
                flags.nounmount = B_TRUE;
				^ ~~~~~~

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Signed-off-by: Brooks Davis <brooks.davis@sri.com>
Closes openzfs#14125

include/libzfs.h

@@ -260,10 +260,10 @@ _LIBZFS_H int zpool_add(zpool_handle_t *, nvlist_t *);
 
 typedef struct splitflags {
 	/* do not split, but return the config that would be split off */
-	int dryrun : 1;
+	unsigned int dryrun : 1;
 
 	/* after splitting, import the pool */
-	int import : 1;
+	unsigned int import : 1;
 	int name_flags;
 } splitflags_t;
 
@@ -690,13 +690,13 @@ _LIBZFS_H int zfs_rollback(zfs_handle_t *, zfs_handle_t *, boolean_t);
 
 typedef struct renameflags {
 	/* recursive rename */
-	int recursive : 1;
+	unsigned int recursive : 1;
 
 	/* don't unmount file systems */
-	int nounmount : 1;
+	unsigned int nounmount : 1;
 
 	/* force unmount file systems */
-	int forceunmount : 1;
+	unsigned int forceunmount : 1;
 } renameflags_t;
 
 _LIBZFS_H int zfs_rename(zfs_handle_t *, const char *, renameflags_t);

lib/libzfs/libzfs_pool.c

@@ -59,9 +59,9 @@
 static boolean_t zpool_vdev_is_interior(const char *name);
 
 typedef struct prop_flags {
-	int create:1;	/* Validate property on creation */
-	int import:1;	/* Validate property on import */
-	int vdevprop:1;	/* Validate property as a VDEV property */
+	unsigned int create:1;	/* Validate property on creation */
+	unsigned int import:1;	/* Validate property on import */
+	unsigned int vdevprop:1; /* Validate property as a VDEV property */
 } prop_flags_t;
 
 /*