ssb: fix boolreturn.cocci warning

./include/linux/ssb/ssb_driver_extif.h:200:8-9:WARNING: return of 0/1 in
function 'ssb_extif_available' with return type bool

Return statements in functions returning bool should use true/false
instead of 1/0.

Generated by: scripts/coccinelle/misc/boolreturn.cocci

Reported-by: Zeal Robot <[e-mail]>
Signed-off-by: Jing Yangyang <[e-mail]>
Signed-off-by: Kalle Valo <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

include/linux/ssb/ssb_driver_extif.h

···
 
 static inline bool ssb_extif_available(struct ssb_extif *extif)
 {
-	return 0;
+	return false;
 }
 
 static inline