remoteproc/mtk_scp: Remove timeout variable from scp_ipi_send()

remoteproc/mtk_scp: Remove timeout variable from scp_ipi_send()

That variable was used twice, but now it's just used once to store
msecs_to_jiffies(wait), fed to wait_event_timeout(): we might as
well remove it for the sake of cleaning up.

This brings no functional changes.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230104115341.320951-3-angelogioacchino.delregno@collabora.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>