Increase buffer size of PS2 protocol

protocol/ps2_usart.c

@@ -287,7 +287,7 @@ static inline void inhibit(void)
 /*--------------------------------------------------------------------
  * Ring buffer to store scan codes from keyboard
  *------------------------------------------------------------------*/
-#define PBUF_SIZE 8
+#define PBUF_SIZE 32
 static uint8_t pbuf[PBUF_SIZE];
 static uint8_t pbuf_head = 0;
 static uint8_t pbuf_tail = 0;