drivers/base: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required.

Most of these files were implicitly getting EXPORT_SYMBOL via
device.h which was including module.h, but that path will be broken
soon.

[ with input from Stephen Rothwell <sfr@canb.auug.org.au> ]

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 59f8ab2..7fa0984 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -19,6 +19,7 @@
 
 #include <linux/device.h>
 #include <linux/kallsyms.h>
+#include <linux/export.h>
 #include <linux/mutex.h>
 #include <linux/pm.h>
 #include <linux/pm_runtime.h>