fix(tree): correct some typos

found using codespell (https://github.com/codespell-project/codespell).

Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Change-Id: I1bfa797e3460adddeefa916bb68e22beddaf6373
diff --git a/lib/xlat_tables_v2/xlat_tables_core.c b/lib/xlat_tables_v2/xlat_tables_core.c
index de57184..3a9c058 100644
--- a/lib/xlat_tables_v2/xlat_tables_core.c
+++ b/lib/xlat_tables_v2/xlat_tables_core.c
@@ -988,7 +988,7 @@
 		     (uintptr_t)mm_last - (uintptr_t)mm_cursor);
 
 	/*
-	 * Check we haven't lost the empty sentinal from the end of the array.
+	 * Check we haven't lost the empty sentinel from the end of the array.
 	 * This shouldn't happen as we have checked in mmap_add_region_check
 	 * that there is free space.
 	 */