apps/system: fix spitool can not send data issue

when use cmd 'spi exch -b 1 -f 3000000 -m 1  -n 0 -w 32 -x 1 1f',
the last character '1f' can not be trans out.

Signed-off-by: yangsong8 <[email protected]>

Author: yangsong8-a1

system/spi/spitool.h

@@ -90,7 +90,11 @@
  * then some.
  */
 
-#define MAX_ARGUMENTS 12
+#ifdef CONFIG_NSH_MAXARGUMENTS
+#define MAX_ARGUMENTS CONFIG_NSH_MAXARGUMENTS
+#else
+#define MAX_ARGUMENTS 16
+#endif
 
 /* Maximum size of one command line */