device.h: cleanup users outside of linux/include (C files)

For files that are actively using linux/device.h, make sure
that they call it out.  This will allow us to clean up some
of the implicit uses of linux/device.h within include/*
without introducing build regressions.

Yes, this was created by "cheating" -- i.e. the headers were
cleaned up, and then the fallout was found and fixed, and then
the two commits were reordered.  This ensures we don't introduce
build regressions into the git history.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/mfd/wm8994-regmap.c b/drivers/mfd/wm8994-regmap.c
index c598ae6..0c0a215 100644
--- a/drivers/mfd/wm8994-regmap.c
+++ b/drivers/mfd/wm8994-regmap.c
@@ -15,6 +15,7 @@
 #include <linux/mfd/wm8994/core.h>
 #include <linux/mfd/wm8994/registers.h>
 #include <linux/regmap.h>
+#include <linux/device.h>
 
 #include "wm8994.h"