powerpc/qe: add polling timeout to qe_issue_cmd()

The qe_issue_cmd() function (Freescale PowerPC QUICC Engine library) polls
on a register until a status bit changes, but does not include a timeout
to handle the situation if the bit never changes.  Change the code to use
the new spin_event_timeout() macro, which simplifies polling on a register
without a timeout.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>