Input: fix ps2/serio module dependency

The ps2 mouse and keyboard drivers use the "serio" framework that they
correctly select in Kconfig, and that in turn depends on the i8042 driver,
which is also allowed to be disabled for architectures that don't have an
i8042.

However, Kconfig also allows i8042 to be built as a module while
the serio framework is built-in, which causes this link error:

drivers/built-in.o: In function `ps2_begin_command':
:(.text+0x26b6cc): undefined reference to `i8042_check_port_owner'
:(.text+0x26b6d4): undefined reference to `i8042_lock_chip'
drivers/built-in.o: In function `ps2_end_command':
:(.text+0x26b734): undefined reference to `i8042_check_port_owner'
:(.text+0x26b73c): undefined reference to `i8042_unlock_chip'

On x86, a specific 'select SERIO_I8042' takes care of it, but
not on the other architecture that potentially have a i8042.

This patch changes the Kconfig logic to ensure that whenever
there is an i8042, it does get used for the serio driver, avoiding
the link error above.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>