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/rlwinm.c b/post/lib_powerpc/rlwinm.c
index 88a28c6..a04ec52 100644
--- a/post/lib_powerpc/rlwinm.c
+++ b/post/lib_powerpc/rlwinm.c
@@ -59,8 +59,7 @@
 	0x0000ff00
    },
 };
-static unsigned int cpu_post_rlwinm_size =
-    sizeof (cpu_post_rlwinm_table) / sizeof (struct cpu_post_rlwinm_s);
+static unsigned int cpu_post_rlwinm_size = ARRAY_SIZE(cpu_post_rlwinm_table);
 
 int cpu_post_test_rlwinm (void)
 {