HSI: fix ssi_waketest() declaration

The ssi_waketest() function definition causes a 'make W=1' warning
because the declaration is hidden away in ssi_protocol.c:

drivers/hsi/controllers/omap_ssi_core.c:147:6: error: no previous prototype for 'ssi_waketest'

Move it into a header file instead.

Fixes: dc7bf5d71868 ("HSI: Introduce driver for SSI Protocol")
Signed-off-by: Arnd Bergmann <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/hsi/clients/ssi_protocol.c

···
 #include <linux/hsi/hsi.h>
 #include <linux/hsi/ssi_protocol.h>
 
-void ssi_waketest(struct hsi_client *cl, unsigned int enable);
-
 #define SSIP_TXQUEUE_LEN	100
 #define SSIP_MAX_MTU		65535
 #define SSIP_DEFAULT_MTU	4000

drivers/hsi/controllers/omap_ssi_core.c

···
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
 #include <linux/delay.h>
+#include <linux/hsi/ssi_protocol.h>
 #include <linux/seq_file.h>
 #include <linux/scatterlist.h>
 #include <linux/interrupt.h>

include/linux/hsi/ssi_protocol.h

···
 void ssip_reset_event(struct hsi_client *master);
 
 int ssip_slave_running(struct hsi_client *master);
+void ssi_waketest(struct hsi_client *cl, unsigned int enable);
 
 #endif /* __LINUX_SSIP_SLAVE_H__ */