Input: add missing exports to fix modular build

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 07f47a0..eb6b13f 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -645,6 +645,7 @@
 	add_timer_randomness(&input_timer_state,
 			     (type << 4) ^ code ^ (code >> 4) ^ value);
 }
+EXPORT_SYMBOL_GPL(add_input_randomness);
 
 void add_interrupt_randomness(int irq)
 {