offset can never be < 0 because it has type size_t.  The driver
currently oopses on insmod if BIOS does not support the interface,
instead of refusing to load.

Signed-off-by: Miloslav Trmac <mitr@volny.cz>

diff -r 88ae680122c0 wistron_btns.c
--- a/drivers/input/misc/wistron_btns.c	Sun Dec 11 21:18:28 2005
+++ b/drivers/input/misc/wistron_btns.c	Sun Jan  8 07:24:44 2006
@@ -114,7 +114,7 @@
 
 	base = ioremap(0xF0000, 0x10000); /* Can't fail */
 	offset = locate_wistron_bios(base);
-	if (offset < 0) {
+	if (offset == (size_t)-1) {
 		printk(KERN_ERR "wistron_btns: BIOS entry point not found\n");
 		iounmap(base);
 		return -ENODEV;