identify_ramdisk_image(): correct typo about return value in comment

identify_ramdisk_image() returns 0 (not -1) if a gzipped ramdisk is found:

	if (buf[0] == 037 && ((buf[1] == 0213) || (buf[1] == 0236))) {
		printk(KERN_NOTICE
		       "RAMDISK: Compressed image found at block %d\n",
		       start_block);
		nblocks = 0;
		^^^^^^^^^^^
		goto done;
	}

	...

done:
	sys_lseek(fd, start_block * BLOCK_SIZE, 0);
	kfree(buf);
	return nblocks;
	^^^^^^^^^^^^^^

Hence correct the typo in the comment, which has existed since the
addition of compressed ramdisk support in 1.3.48.

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>