b44 WOL setup: one-bit-off stack corruption kernel panic fix

About 50% of shutdowns of b44 Ethernet adapter ends by kernel panic
with kernels compiled with stack-protector.

Checking b44_magic_pattern() return values, one call of
b44_magic_pattern() returns 127. It means, that set_bit(128, pmask)
was called on line 1509. It means that bit 0 of 17th byte of pmask was
overwritten. But pmask has only 16 bytes. Stack corruption happens.
 
It seems that set_bit() on line 1509 always writes one bit off.

The fix does not only solve the stack corruption, but also makes Wake
On LAN working on my onboard B44 on Asus A7V-333X mainboard.

It seems that this problem affects all kernel versions since commit
725ad800 ([PATCH] b44: add wol for old nic) on 2006-06-20.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>