i2c: completion header cleanups

i2c-core and i2c-isa use completions without including
<linux/completion.h>. Fix it.

i2c-powermac includes <linux/completion.h> but doesn't use any
completion. Fix it.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Brownell <david-b@pacbell.net>
diff --git a/drivers/i2c/busses/i2c-isa.c b/drivers/i2c/busses/i2c-isa.c
index 8ed59a2..5f33bc9 100644
--- a/drivers/i2c/busses/i2c-isa.c
+++ b/drivers/i2c/busses/i2c-isa.c
@@ -39,6 +39,7 @@
 #include <linux/i2c.h>
 #include <linux/i2c-isa.h>
 #include <linux/platform_device.h>
+#include <linux/completion.h>
 
 static u32 isa_func(struct i2c_adapter *adapter);