soc: ti: fix wkup_m3_rproc_boot_thread return type

soc: ti: fix wkup_m3_rproc_boot_thread return type

The wkup_m3_rproc_boot_thread() function uses a nonstandard prototype,
which broke after Eric's recent cleanup:

drivers/soc/ti/wkup_m3_ipc.c: In function 'wkup_m3_rproc_boot_thread':
drivers/soc/ti/wkup_m3_ipc.c:429:16: error: 'return' with a value, in function returning void [-Werror=return-type]
  429 |         return 0;
      |                ^
drivers/soc/ti/wkup_m3_ipc.c:416:13: note: declared here
  416 | static void wkup_m3_rproc_boot_thread(struct wkup_m3_ipc *m3_ipc)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~

Change it to the normal prototype as it should have been from the
start.

Fixes: f2dd62672d0c ("exit/kthread: Have kernel threads return instead of calling do_exit")
Fixes: 611b646b6a3f ("soc: ti: Add wkup_m3_ipc driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lkml.kernel.org/r/20211105075119.2327190-1-arnd@kernel.org
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>