soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

BugLink: https://bugs.launchpad.net/bugs/1862203
[ Upstream commit 03729cfa0d543bc996bf959e762ec999afc8f3d2 ]

Any user of wkup_m3_ipc calls wkup_m3_ipc_get to get a handle and this
checks the value of the static variable m3_ipc_state to see if the
wkup_m3 is ready. Currently this is populated during probe before
rproc_boot has been called, meaning there is a window of time that
wkup_m3_ipc_get can return a valid handle but the wkup_m3 itself is not
ready, leading to invalid IPC calls to the wkup_m3 and system
instability.

To avoid this, move the population of the m3_ipc_state variable until
after rproc_boot has succeeded to guarantee a valid and usable handle
is always returned.

Reported-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>