increase the uart ring buffer size

must be be a power of 2, and should be at least as large as the largest
transfer that we might be waiting for - revisit this, is 256 enough?

Change-Id: Id4b4691dd32d465f627ba42c0ba3d509dcf8f42c
diff --git a/sysmoOCTSIM/driver_init.c b/sysmoOCTSIM/driver_init.c
index 620ed6c..c373dc2 100644
--- a/sysmoOCTSIM/driver_init.c
+++ b/sysmoOCTSIM/driver_init.c
@@ -12,25 +12,25 @@
 #include <hal_init.h>
 
 /*! The buffer size for USART */
-#define SIM0_BUFFER_SIZE 16
+#define SIM0_BUFFER_SIZE 512
 
 /*! The buffer size for USART */
-#define SIM1_BUFFER_SIZE 16
+#define SIM1_BUFFER_SIZE 512
 
 /*! The buffer size for USART */
-#define SIM2_BUFFER_SIZE 16
+#define SIM2_BUFFER_SIZE 512
 
 /*! The buffer size for USART */
-#define SIM3_BUFFER_SIZE 16
+#define SIM3_BUFFER_SIZE 512
 
 /*! The buffer size for USART */
-#define SIM4_BUFFER_SIZE 16
+#define SIM4_BUFFER_SIZE 512
 
 /*! The buffer size for USART */
-#define SIM5_BUFFER_SIZE 16
+#define SIM5_BUFFER_SIZE 512
 
 /*! The buffer size for USART */
-#define SIM6_BUFFER_SIZE 16
+#define SIM6_BUFFER_SIZE 512
 
 /*! The buffer size for USART */
 #define UART_DEBUG_BUFFER_SIZE 256