Add 64-bit data support for memory commands

Add 64-bit data for memory commands, such as md, mw, mm, cmp. The new
size ".q " is introduced.

For 64-bit architecture, 64-bit data is enabled by default, by detecting
compiler __LP64__. It is optional for other architectures.

Signed-off-by: York Sun <yorksun@freescale.com>

common/command.c

@@ -421,6 +421,10 @@ int cmd_get_data_size(char* arg, int default_size)
 			return 2;
 		case 'l':
 			return 4;
+#ifdef CONFIG_SYS_SUPPORT_64BIT_DATA
+		case 'q':
+			return 8;
+#endif
 		case 's':
 			return -2;
 		default: