sepolicy: allow dump page_pinner

Provide necessary sepolicy for dumpreport to access page_pinner
information in /sys/kernel/debug/page_pinner/{longterm_pinner,
alloc_contig_failed}

Bug: 226956571
Test: Run "adb bugreport <zip>" and verify it contains the output
      from page_pinner.
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: I7b00d4930fbaa2061537cd8c84616c1053c829cf