Input: ambakmi - fix timeout handling in amba_kmi_write()

With a postfix decrement timeleft reaches -1 rather than 0,
but after the loop it is tested to have become 0.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>