drm/xe: Fix memory leak when handling pagefault vma

drm/xe: Fix memory leak when handling pagefault vma

When the pagefault handling code was moved to a new file, an extra
drm_exec_init() was added to the VMA path. This call is unnecessary because
xe_validation_ctx_init() already performs a drm_exec_init(), resulting in a
memory leak reported by kmemleak.

Remove the redundant drm_exec_init() from the VMA pagefault handling code.

Fixes: fb544b844508 ("drm/xe: Implement xe_pagefault_queue_work")
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Stuart Summers <stuart.summers@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: intel-xe@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20251120161435.3674556-1-mika.kuoppala@linux.intel.com