Publish libshare protocols, use enum-based API

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13165

lib/libshare/os/linux/nfs.c

@@ -481,9 +481,7 @@ nfs_commit_shares(void)
 	return (libzfs_run_process(argv[0], argv, 0));
 }
 
-sa_fstype_t libshare_nfs_type = {
-	.protocol = "nfs",
-
+const sa_fstype_t libshare_nfs_type = {
 	.enable_share = nfs_enable_share,
 	.disable_share = nfs_disable_share,
 	.is_shared = nfs_is_shared,

lib/libshare/os/linux/smb.c

@@ -363,9 +363,7 @@ smb_update_shares(void)
 	return (0);
 }
 
-sa_fstype_t libshare_smb_type = {
-	.protocol = "smb",
-
+const sa_fstype_t libshare_smb_type = {
 	.enable_share = smb_enable_share,
 	.disable_share = smb_disable_share,
 	.is_shared = smb_is_share_active,