x86/resctrl: Fix typos in the mba_sc mount option

The user can control the MBA memory bandwidth in MBps (Mega
Bytes per second) units of the MBA Software Controller (mba_sc)
by using the "mba_MBps" mount option. For details, see
Documentation/x86/resctrl_ui.txt.

However, commit

  23bf1b6b ("kernfs, sysfs, cgroup, intel_rdt: Support fs_context")

changed the mount option name from "mba_MBps" to "mba_mpbs" by mistake.

Change it back from to "mba_MBps" because it is user-visible, and
correct "Opt_mba_mpbs" spelling to "Opt_mba_mbps".

 [ bp: massage commit message. ]

Fixes: 23bf1b6b

 ("kernfs, sysfs, cgroup, intel_rdt: Support fs_context")
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: dhowells@redhat.com
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: pei.p.jia@intel.com
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/1553896238-22130-1-git-send-email-xiaochen.shen@intel.com