powerpc: add export.h to files making use of EXPORT_SYMBOL

With module.h being implicitly everywhere via device.h, the absence
of explicitly including something for EXPORT_SYMBOL went unnoticed.
Since we are heading to fix things up and clean module.h from the
device.h file, we need to explicitly include these files now.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/powerpc/sysdev/dcr.c b/arch/powerpc/sysdev/dcr.c
index bb44aa9..1bd0eba 100644
--- a/arch/powerpc/sysdev/dcr.c
+++ b/arch/powerpc/sysdev/dcr.c
@@ -20,6 +20,7 @@
 #undef DEBUG
 
 #include <linux/kernel.h>
+#include <linux/export.h>
 #include <asm/prom.h>
 #include <asm/dcr.h>