drivers: dma: dw: Add power management state check in get_status

Add power management state validation in dw_dma_get_status() to ensure
the device is in active state before attempting to read DMA status.
Returns -EINVAL if device is not active, preventing potential issues
when accessing hardware registers while device is suspended.

Signed-off-by: Adrian Bonislawski <adrian.bonislawski@intel.com>