greybus: protocol: switch gb_protocol_register() to return an int

We will want to return this value as a return value for module_init()
and bool does not play well with module_init().  So make it a "real"
error value and return int and fix up all callers of the function.

Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
diff --git a/drivers/staging/greybus/pwm-gb.c b/drivers/staging/greybus/pwm-gb.c
index c505f1d..5f02e78 100644
--- a/drivers/staging/greybus/pwm-gb.c
+++ b/drivers/staging/greybus/pwm-gb.c
@@ -319,7 +319,7 @@
 	.request_recv		= NULL, /* no incoming requests */
 };
 
-bool gb_pwm_protocol_init(void)
+int gb_pwm_protocol_init(void)
 {
 	return gb_protocol_register(&pwm_protocol);
 }