LU-8066 ptlrpc: move simple req_buffer_* to sysfs

LU-8066 ptlrpc: move simple req_buffer_* to sysfs

Some of the ptlrpc req_buffer_* debugfs files are simple
enough to move to sysfs.

Test-Parameters: trivial
Change-Id: I0feb554de2d4cdabe1c9bc4e5cf1fc700d0ea679
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58498
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>