drm/i915/hdcp: check streams[] bounds before overflow

drm/i915/hdcp: check streams[] bounds before overflow

The data->streams[] overflow check is done after the buffer overflow has
already happened. Move the overflow check before the write.

Side note, emitting a warning splat with a backtrace might be overkill
here, but prefer not changing the behaviour other than not doing the
overrun.

Discovered using AI-assisted static analysis confirmed by Intel Product
Security.

Reported-by: Martin Hodo <martin.hodo@intel.com>
Fixes: e03187e12cae ("drm/i915/hdcp: MST streams support in hdcp port_data")
Cc: stable@vger.kernel.org # v5.12+
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patch.msgid.link/20260625170304.1104723-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 9284ab3b6e776c315883ac2611283d263c9460fd)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>