UPSTREAM: psi: fix reference to kernel commandline enable

UPSTREAM: psi: fix reference to kernel commandline enable

The kernel commandline parameter named in CONFIG_PSI_DEFAULT_DISABLED
help text contradicts the documentation in kernel-parameters.txt, and
the code.  Fix that.

Link: http://lkml.kernel.org/r/20181203213416.GA12627@cmpxchg.org
Fixes: e0c274472d ("psi: make disabling/enabling easier for vendor kernels")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 428a1cb4baeb9e5c7feda93af7372ba6d2491558)

Bug: 127712811
Test: lmkd in PSI mode
Change-Id: I592b66d6542f4fa7c2b6eb9f60a5dd43bcfbabf3
Signed-off-by: Suren Baghdasaryan <surenb@google.com>