post: use ARRAY_SIZE

We've got a handy dandy macro already for calculating the number of
elements in an array, so use it.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/post/lib_powerpc/twox.c b/post/lib_powerpc/twox.c
index d6714f9..88140bf 100644
--- a/post/lib_powerpc/twox.c
+++ b/post/lib_powerpc/twox.c
@@ -81,8 +81,7 @@
 	12
     },
 };
-static unsigned int cpu_post_twox_size =
-    sizeof (cpu_post_twox_table) / sizeof (struct cpu_post_twox_s);
+static unsigned int cpu_post_twox_size = ARRAY_SIZE(cpu_post_twox_table);
 
 int cpu_post_test_twox (void)
 {