Input: lifebook - use "static inline" instead of "inline" in lifebook.h

For functions defined in header files we should use static inline rather
than inline, which breaks under the latest upstream gcc (which is really
gcc issue, but static inline is better suited regardless).

The related error (with allmodconfig under tile):

    MODPOST 4002 modules
  ERROR: "lifebook_detect" [drivers/input/mouse/psmouse.ko] undefined!

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>