ioe_rpmsg: use rptun_wait/post to resolve deadlock with usrsock

[GUIDINGLI]

Summary

ioe_rpmsg: use rptun_wait/post to resolve deadlock with usrsock

This depends on:
#5847

Impact

ioe_rpmsg

Testing

VELA

[pkarashchenko]

Changes looks good, but please fix the build

[pkarashchenko]

ioexpander/ioe_rpmsg.c: In function 'ioe_rpmsg_wait_ready':
Error: ioexpander/ioe_rpmsg.c:240:13: error: implicit declaration of function 'rpmsg_wait' [-Werror=implicit-function-declaration]
  240 |       ret = rpmsg_wait(ept, &priv->sem);
      |             ^~~~~~~~~~
Error: ioexpander/ioe_rpmsg.c:246:7: error: implicit declaration of function 'rpmsg_post' [-Werror=implicit-function-declaration]
  246 |       rpmsg_post(ept, &priv->sem);
      |       ^~~~~~~~~~

[xiaoxiang781216]

@liguiding please rebase to your code.