Fix typos in module/zfs/

Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net>
Closes #9240

module/zfs/zfs_vnops.c

@@ -889,7 +889,7 @@ zfs_write(struct inode *ip, uio_t *uio, int ioflag, cred_t *cr)
 		 * Clear Set-UID/Set-GID bits on successful write if not
 		 * privileged and at least one of the execute bits is set.
 		 *
-		 * It would be nice to to this after all writes have
+		 * It would be nice to do this after all writes have
 		 * been done, but that would still expose the ISUID/ISGID
 		 * to another app after the partial write is committed.
 		 *
@@ -4378,7 +4378,7 @@ top:
 		uint64_t txtype = TX_LINK;
 		/*
 		 * tmpfile is created to be in z_unlinkedobj, so remove it.
-		 * Also, we don't log in ZIL, be cause all previous file
+		 * Also, we don't log in ZIL, because all previous file
 		 * operation on the tmpfile are ignored by ZIL. Instead we
 		 * always wait for txg to sync to make sure all previous
 		 * operation are sync safe.
@@ -4638,7 +4638,7 @@ zfs_dirty_inode(struct inode *ip, int flags)
 
 #ifdef I_DIRTY_TIME
 	/*
-	 * This is the lazytime semantic indroduced in Linux 4.0
+	 * This is the lazytime semantic introduced in Linux 4.0
 	 * This flag will only be called from update_time when lazytime is set.
 	 * (Note, I_DIRTY_SYNC will also set if not lazytime)
 	 * Fortunately mtime and ctime are managed within ZFS itself, so we