firmware: imx: scu-pd: Add IRQSTR_DSP PD range

The DSP interrupt steer gathers interrupts from the system
and can be used to steer them to DSP.

Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>