Input: i8042 - fix refount leak on sparc

In i8042_platform_init() and i8042_platform_exit(), we should call
of_node_put() for the reference 'root' returned by
of_find_node_by_path() which has increased the refcount.

Fixes: f57caaef

 ("[SERIO] i8042-sparcio.h: Convert to of_driver framework.")
Signed-off-by: Liang He <windhl@126.com>
Link: https://lore.kernel.org/r/20220711064300.358757-1-windhl@126.com
[dtor: rearranged i8042_is_mr_coffee() a bit]
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>