ALSA: pcsp: Include appropriate header file in pcsp/pcsp_input.c

Include appropriate header file in drivers/pcsp/pcsp_input.c because it
defines function whose prototype definitions are present in
drivers/pcsp/pcsp_input.h.

This eliminates the following warning in drivers/pcsp/pcsp_input.c:
sound/drivers/pcsp/pcsp_input.c:42:6: warning: no previous prototype for ‘pcspkr_stop_sound’ [-Wmissing-prototypes]
sound/drivers/pcsp/pcsp_input.c:80:5: warning: no previous prototype for ‘pcspkr_input_init’ [-Wmissing-prototypes]
sound/drivers/pcsp/pcsp_input.c:110:5: warning: no previous prototype for ‘pcspkr_input_remove’ [-Wmissing-prototypes]

Signed-off-by: Rashika Kheria <[e-mail]>
Reviewed-by: Josh Triplett <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/drivers/pcsp/pcsp_input.c

···
 #include <linux/input.h>
 #include <asm/io.h>
 #include "pcsp.h"
+#include "pcsp_input.h"
 
 static void pcspkr_do_sound(unsigned int count)
 {