drm/xe/oa: Fix potential UAF in xe_oa_add_config_ioctl()

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

drm/xe/oa: Fix potential UAF in xe_oa_add_config_ioctl()

In xe_oa_add_config_ioctl(), we accessed oa_config->id after dropping metrics_lock. Since this lock protects the lifetime of oa_config, an attacker could guess the id and call xe_oa_remove_config_ioctl() with perfect timing, freeing oa_config before we dereference it, leading to a potential use-after-free.

Fix this by caching the id in a local variable while holding the lock.

v2: (Matt A) - Dropped mutex_unlock(&oa->metrics_lock) ordering change from xe_oa_remove_config_ioctl()

(cherry picked from commit 28aeaed130e8e587fd1b73b6d66ca41ccc5a1a31)