MIPS: Alchemy: In plat_time_init() t reaches -1, tested: 0

With a postfix decrement t reaches -1 rather than 0, so the fall-back will
not occur.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: mano@roarinelk.homelinux.net
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>