Increase buffer size

By default, more than 2K of SRAM are available. Using some of that to increase a few buffer sizes.

Marlin/Configuration_adv.h

@@ -879,8 +879,8 @@
 // @section serial
 
 // The ASCII buffer for serial input
-#define MAX_CMD_SIZE 96
-#define BUFSIZE 4
+#define MAX_CMD_SIZE 128
+#define BUFSIZE 8
 
 // Transmission to Host Buffer Size
 // To save 386 bytes of PROGMEM (and TX_BUFFER_SIZE+3 bytes of RAM) set to 0.
@@ -889,13 +889,13 @@
 // For debug-echo: 128 bytes for the optimal speed.
 // Other output doesn't need to be that speedy.
 // :[0, 2, 4, 8, 16, 32, 64, 128, 256]
-#define TX_BUFFER_SIZE 0
+#define TX_BUFFER_SIZE 256
 
 // Host Receive Buffer Size
 // Without XON/XOFF flow control (see SERIAL_XON_XOFF below) 32 bytes should be enough.
 // To use flow control, set this buffer size to at least 1024 bytes.
 // :[0, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048]
-//#define RX_BUFFER_SIZE 32
+#define RX_BUFFER_SIZE 256
 
 #if RX_BUFFER_SIZE >= 1024
   // Enable to have the controller send XON/XOFF control characters to