Make ReservationOffsetTable NotAllocated when DirectMap allocation with kReturnNull fails.

Bug: 502299262
Change-Id: Iaa82d9eb5bcbd0740101c1dd7e7c6e772d60e98b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7759816
Reviewed-by: Keishi Hattori <keishi@chromium.org>
Commit-Queue: Takashi Sakamoto <tasak@google.com>
Cr-Commit-Position: refs/heads/main@{#1614224}
NOKEYCHECK=True
GitOrigin-RevId: 1dcf1dbe32fc0637ec18f1c7b3e6f104f419cf6e