powerpc/rtas: rtas_ibm_suspend_me -> rtas_ibm_suspend_me_unsafe

The pseries partition suspend sequence requires that all active CPUs
call H_JOIN, which suspends all but one of them with interrupts
disabled. The "chosen" CPU is then to call ibm,suspend-me to complete
the suspend. Upon returning from ibm,suspend-me, the chosen CPU is to
use H_PROD to wake the joined CPUs.

Using on_each_cpu() for this, as rtas_ibm_suspend_me() does to
implement partition migration, is susceptible to deadlock with other
users of on_each_cpu() and with users of stop_machine APIs. The
callback passed to on_each_cpu() is not allowed to synchronize with
other CPUs in the way it is used here.

Complicating the fix is the fact that rtas_ibm_suspend_me() also
occupies the function name that should be used to provide a more
conventional wrapper for ibm,suspend-me. Rename rtas_ibm_suspend_me()
to rtas_ibm_suspend_me_unsafe() to free up the name and indicate that
it should not gain users.

Signed-off-by: Nathan Lynch <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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