cpu/hotplug: Remove disable_nonboot_cpus()

The single user could have called freeze_secondary_cpus() directly.

Since this function was a source of confusion, remove it as it's
just a pointless wrapper.

While at it, rename enable_nonboot_cpus() to thaw_secondary_cpus() to
preserve the naming symmetry.

Done automatically via:

	git grep -l enable_nonboot_cpus | xargs sed -i 's/enable_nonboot_cpus/thaw_secondary_cpus/g'

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Link: https://lkml.kernel.org/r/20200430114004.17477-1-qais.yousef@arm.com

Documentation/power/suspend-and-cpuhotplug.rst

@@ -48,7 +48,7 @@ More details follow::
                                         |
                                         |
                                         v
-                              disable_nonboot_cpus()
+                              freeze_secondary_cpus()
                                    /* start */
                                         |
                                         v
@@ -83,7 +83,7 @@ More details follow::
                             Release cpu_add_remove_lock
                                         |
                                         v
-                       /* disable_nonboot_cpus() complete */
+                       /* freeze_secondary_cpus() complete */
                                         |
                                         v
                                    Do suspend
@@ -93,7 +93,7 @@ More details follow::
 Resuming back is likewise, with the counterparts being (in the order of
 execution during resume):
 
-* enable_nonboot_cpus() which involves::
+* thaw_secondary_cpus() which involves::
 
    |  Acquire cpu_add_remove_lock
    |  Decrease cpu_hotplug_disabled, thereby enabling regular cpu hotplug