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>

init/Kconfig

@@ -515,8 +515,8 @@ config PSI_DEFAULT_DISABLED
 	depends on PSI
 	help
 	  If set, pressure stall information tracking will be disabled
-	  per default but can be enabled through passing psi_enable=1
-	  on the kernel commandline during boot.
+	  per default but can be enabled through passing psi=1 on the
+	  kernel commandline during boot.
 
 endmenu # "CPU/Task time and stats accounting"