Fix: openamp_arduino: increase number of rpmsg buffers to 64.

As noted by @iabdalkader in #44 (comment).

See also https://github.com/arduino/ArduinoCore-mbed/pull/830/files#diff-1d9831965651ccab301436166b9aa923da8d54b384d6f1078538f98425f7f0ee.

Author: aentinger

libraries/openamp_arduino/src/openamp_conf.h

@@ -158,7 +158,7 @@ extern int __OPENAMP_region_end__[];
 #define VRING_BUFF_ADDRESS      (SHM_START_ADDRESS + 0x2000)
 #define VRING_BUFF_SIZE         (SHM_SIZE - 0x2000)
 #define VRING_ALIGNMENT         32
-#define VRING_NUM_BUFFS         16   /* number of rpmsg buffers */
+#define VRING_NUM_BUFFS         64   /* number of rpmsg buffers */
 
 /* Fixed parameter */
 #define NUM_RESOURCE_ENTRIES    2