arm64/mpam: update reminder message about MBHDL option

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I91YTV


CVE: NA

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Corrected debugging reminder information about MBHDL option of
schemata interface.

  # echo "MBHDL:1=2" > schemata
  -bash: echo: write error: Invalid argument
  # cat info/last_cmd_status
  MB value 2 exceed 1

Signed-off-by: Zeng Heng <zengheng4@huawei.com>