Input: i8042 - try to get stable CTR value when initializing

If user presses keys while i8042 is being initialized there is a chance
that keyboard data will be mistaken for results of Read Control Register
command causing futher troubles. Work around this issue by reading CTR
several times and stop when we get matching results.

Reported-and-tested-by: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>