xsysace: use platform_get_resource() and platform_get_irq_optional()

Use platform_get_resource() to fetch the memory resource and
platform_get_irq_optional() to get optional IRQ instead of
open-coded variants.

IRQ is not supposed to be changed at runtime, so there is
no functional change in ace_fsm_yieldirq().

On the other hand we now take first resources instead of last ones
to proceed. I can't imagine how broken should be firmware to have
a garbage in the first resource slots. But if it the case, it needs
to be documented.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>