cmd: pxe: Increase maximum path length

On NixOS, cross compiled kernels have long suffixes that cause them to
exceed the current maximum path length. The PXE/TFTP max path length is
used for extlinux.conf support as well, which is where this problem
usually manifest's itself.
Signed-off-by: NBen Wolsieffer <benwolsieffer@gmail.com>
Acked-by: NJoe Hershberger <joe.hershberger@ni.com>

cmd/pxe_utils.c

@@ -22,7 +22,7 @@
 
 #include "pxe_utils.h"
 
-#define MAX_TFTP_PATH_LEN 127
+#define MAX_TFTP_PATH_LEN 512
 
 bool is_pxe;