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/xlat_tables_common.c b/lib/xlat_tables/xlat_tables_common.c
index 71273cb..e2c8370 100644
--- a/lib/xlat_tables/xlat_tables_common.c
+++ b/lib/xlat_tables/xlat_tables_common.c
@@ -161,7 +161,7 @@
 	/* Make room for new region by moving other regions up by one place */
 	(void)memmove(mm + 1, mm, (uintptr_t)mm_last - (uintptr_t)mm);
 
-	/* 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 */
 	assert(mm_last->size == 0U);
 
 	mm->base_pa = base_pa;