Fix a masking bug in the 6pack driver.

Looks like a broken masking to me, binary not is used where bitwise
not was intended.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>