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.