drm graphics drivers -- potential information disclusure via local access

Intel reports:

.A potential security vulnerability in Intel® Processor Graphics
may allow information disclosure. Intel is releasing software
updates to mitigate this potential vulnerability.
Description: Insufficient control flow in certain data
structures for some Intel® Processors with Intel® Processor
Graphics may allow an unauthenticated user to potentially enable
information disclosure via local access.
This patch provides mitigation for Gen9 hardware only. Patches
for Gen7 and Gen7.5 will be provided later. Note that Gen8 is not
impacted due to a previously implemented workaround. The mitigation
involves using an existing hardware feature to forcibly clear down
all EU state at each context switch.