lpc2k_pgm: fix build warnings

GCC now warns when snprintf()ing a buffer that, together with the
format string, might be larger than the destination buffer.

To fix this increase the size of the destination buffer so that
the source buffer and the format string will always fit - 32 bytes
are enough.

boards/common/msba2/tools/src/download.c

@@ -245,7 +245,7 @@ hardware you may be using.  Thanks :-)\r\n"
 
 static void download_main(int event)
 {
-    char buf[4096];
+    char buf[4096 + 32];
     unsigned char bytes[256];
     double xtal;
     int n;