add cortex-v7a support

How To Run:
    see TencentOS-tiny\board\ALPHA_I.MX_emmc_256ddr\README.md

TODO Next:
1. VFP support
2. fault diagnosis support
3. qemu vexpress ca9 support
4. raspberry pi support
5. SMP support

components/shell/tos_shell.c

@@ -101,7 +101,7 @@ __STATIC__ void shell_cmd_process(void)
             ++pos;
         }
 
-        while ((*pos == ' ' || *pos == '\t') && *pos) {
+        while (*pos == ' ' || *pos == '\t') {
             *pos++ = '\0';
         }