blackfin: add module.h to files implicitly expecting to use it.

Its presence was implicit everywhere, but we are aiming to fix that,
so call out the users explicitly.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/blackfin/mach-common/cpufreq.c b/arch/blackfin/mach-common/cpufreq.c
index 85dc6d6..2e6eefd 100644
--- a/arch/blackfin/mach-common/cpufreq.c
+++ b/arch/blackfin/mach-common/cpufreq.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/cpufreq.h>