Revert "media: iris: Add sanity check for stop streaming"

In the Linux kernel, the following vulnerability has been resolved:

Revert "media: iris: Add sanity check for stop streaming"

This reverts commit ad699fa78b59241c9d71a8cafb51525f3dab04d4.

Revert the check that skipped stop_streaming when the instance was in

IRIS_INST_ERROR, as it caused multiple regressions:

1. Buffers were not returned to vb2 when the instance was already in

error state, triggering warnings in the vb2 core because buffer

completion was skipped.

2. If a session failed early (e.g. unsupported configuration), the

instance transitioned to IRIS_INST_ERROR. When userspace attempted

to stop streaming for cleanup, stop_streaming was skipped due to the

added check, preventing proper teardown and leaving the firmware

in an inconsistent state.