Input: i8042 - fix warning on non-x86 builds

Commit c18bab80 ("Input: i8042 - non-x86 build fix") introduced the
following warning on non-x86 builds:

    drivers/input/serio/i8042.c: In function 'i8042_probe':
    drivers/input/serio/i8042.c:1154: warning: unused variable 'param'

Fix this by moving the parameter variable declaration into the #ifdef too.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>