LU-17001 pcc: fix the build failures for mmap_conv

LU-17001 pcc: fix the build failures for mmap_conv

PCC has implemented mmap page conversion for performance reason.
However, it is not stable, and disabled by default.

The Lustre build meets some failures against the newer kernel such
as Ubuntu 2204 kernel 6.2.0-26-generic.
The reason is that @pagevec_lookup and @add_to_page_cache_locked
are removed and no longer exported by the kernel.

This patch gives a simple solution. It disables the mmap_conv
option for PCC and does not perform mmap page conversion for
the newer kernel without @add_to_page_cache_locked exported.

Change-Id: Ie314830f225848b7f888709ad000fd7d36d3c0b2
Signed-off-by: Qian Yingjin <qian@ddn.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/51798
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>