accel/ivpu: Make ivpu_pm_init() void

ivpu_pm_init() does not return any error, make it void.

Reviewed-by: Karol Wachowski <karol.wachowski@linux.intel.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230901094957.168898-4-stanislaw.gruszka@linux.intel.com