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/rlwnm.c b/post/lib_powerpc/rlwnm.c
index 60bcb6d..764fe0c 100644
--- a/post/lib_powerpc/rlwnm.c
+++ b/post/lib_powerpc/rlwnm.c
@@ -60,8 +60,7 @@
 	0x0000ff00
    },
 };
-static unsigned int cpu_post_rlwnm_size =
-    sizeof (cpu_post_rlwnm_table) / sizeof (struct cpu_post_rlwnm_s);
+static unsigned int cpu_post_rlwnm_size = ARRAY_SIZE(cpu_post_rlwnm_table);
 
 int cpu_post_test_rlwnm (void)
 {