* fs/cpio.c (grub_cpio_find_file): Return GRUB_ERR_NONE
(and set *ofs = 0) instead of GRUB_ERR_FILE_NOT_FOUND on
last block of a cpio or tar stream.
Check for "TRAILER!!!" instead of any empty data
block to detect last block of a cpio stream.
(grub_cpio_dir): Fix constness of variable np.
(grub_cpio_open): Return GRUB_ERR_FILE_NOT_FOUND if
cpio or tar trailer is detected. This fixes a crash
on open of a non existing file.
