Fixes the allocation size when sending a neighbor solicitation packet to avoid having to always reallocate the buffer. (#1039)

Co-authored-by: Emil Popov <epopov@cardinalkinetic.com>

Author: evpopov

source/FreeRTOS_ARP.c

@@ -588,7 +588,7 @@ BaseType_t xCheckRequiresARPResolution( const NetworkBufferDescriptor_t * pxNetw
                                NetworkBufferDescriptor_t * pxTempBuffer;
                                size_t uxNeededSize;
 
-                               uxNeededSize = ipSIZE_OF_ETH_HEADER + ipSIZE_OF_IPv6_HEADER + sizeof( ICMPRouterSolicitation_IPv6_t );
+                               uxNeededSize = sizeof( ICMPPacket_IPv6_t );
                                pxTempBuffer = pxGetNetworkBufferWithDescriptor( BUFFER_FROM_WHERE_CALL( 199 ) uxNeededSize, 0U );
 
                                if( pxTempBuffer != NULL )