UBIFS: correct spelling of "thrice".

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
diff --git a/fs/ubifs/find.c b/fs/ubifs/find.c
index c70c767..adee7b5 100644
--- a/fs/ubifs/find.c
+++ b/fs/ubifs/find.c
@@ -290,7 +290,7 @@
 		idx_lp = idx_heap->arr[0];
 		sum = idx_lp->free + idx_lp->dirty;
 		/*
-		 * Since we reserve trice as more space for the index than it
+		 * Since we reserve thrice as much space for the index than it
 		 * actually takes, it does not make sense to pick indexing LEBs
 		 * with less than, say, half LEB of dirty space. May be half is
 		 * not the optimal boundary - this should be tested and