[doc] Issue in "I/O Scheduler Tuning"

[Al-github-bs]

I/O Scheduler Tuning:
https://documentation.suse.com/sbp/all/single-html/SBP-performance-tuning/#sec-io-scheduler-tuning

Hello,
This document needs updating. There is a significant behavior change to the defaults that is not in the release notes but is described in documentation. Both the available and default I/O schedulers changed with sles15sp2 (kernel 5.3.x) [1] which differs from sles12sp5 (kernel 4.12.x) [2] & sles15sp1 (kernel 4.12.x) [3] . Per the documentation the I/O scheduler defaults were changed from DEADLINE (HDD) and CFQ (SSD) to BFQ (HDD) & MQ-DEADLINE or none (SSD).

[1] https://documentation.suse.com/sles/15-SP2/html/SLES-all/cha-tuning-io.html#cha-tuning-io-switch
[2] https://documentation.suse.com/sles/12-SP5/html/SLES-all/cha-tuning-io.html#cha-tuning-io-switch
[3] https://documentation.suse.com/sles/15-SP1/html/SLES-all/cha-tuning-io.html#cha-tuning-io-switch