staging: Add export.h for THIS_MODULE/EXPORT_SYMBOL to drivers/staging users.

Lots of drivers have in the past expected the presence of basic things
like THIS_MODULE and EXPORT_SYMBOL.  With the header cleanup, they wont
have these.  Call out the include explicitly.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/staging/solo6x10/g723.c b/drivers/staging/solo6x10/g723.c
index 59274bf..2cd0de2 100644
--- a/drivers/staging/solo6x10/g723.c
+++ b/drivers/staging/solo6x10/g723.c
@@ -23,6 +23,7 @@
 #include <linux/kthread.h>
 #include <linux/slab.h>
 #include <linux/freezer.h>
+#include <linux/export.h>
 #include <sound/core.h>
 #include <sound/initval.h>
 #include <sound/pcm.h>