ANDROID: mm: page_pinner: remove dump_page_pinner

This patch removes dump_page_pinner since it was not useful(IOW,
the page_pinner buffer to keep the history is enough).

This patch also changes mismatched printf format specifier.

Bug: 218731671
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: I80c6f5ad656b3b0d27a50eabff4d1382559aa105