Add missing checks for unsupported features

After 35ec517 it has become possible to import ZFS pools witn an
active org.illumos:edonr feature on FreeBSD, leading to a panic.

In addition, "zpool status" reported all pools without edonr
as upgradable and "zpool upgrade -v" reported edonr in the list
of upgradable features.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Martin Matuska <mm@FreeBSD.org>
Closes #11653

module/zcommon/zfeature_common.c

@@ -100,6 +100,8 @@ zfeature_is_supported(const char *guid)
 
 	for (spa_feature_t i = 0; i < SPA_FEATURES; i++) {
 		zfeature_info_t *feature = &spa_feature_table[i];
+		if (!feature->fi_zfs_mod_supported)
+			continue;
 		if (strcmp(guid, feature->fi_guid) == 0)
 			return (B_TRUE);
 	}