rpmsgfs: do NOT access the pointer when do remote ioctl

[GUIDINGLI]

Summary

rpmsgfs: do NOT access the pointer when do remote ioctl

rpmsgfs/rename: fix bug about pathname align with 8bytes

This depends on:
#5892

Impact

rpmsgfs

Testing

VELA

[pkarashchenko]

rpmsgfs/rpmsgfs_client.c: In function 'rpmsgfs_ioctl_handler':
Error: rpmsgfs/rpmsgfs_client.c:176:3: error: implicit declaration of function 'rpmsg_post' [-Werror=implicit-function-declaration]
  176 |   rpmsg_post(ept, &cookie->sem);
      |   ^~~~~~~~~~
rpmsgfs/rpmsgfs_client.c: In function 'rpmsgfs_client_ioctl':
Error: rpmsgfs/rpmsgfs_client.c:506:9: error: implicit declaration of function 'rpmsgfs_get_tx_payload_buffer'; did you mean 'rpmsg_get_tx_payload_buffer'? [-Werror=implicit-function-declaration]
  506 |   msg = rpmsgfs_get_tx_payload_buffer(priv, &space);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |         rpmsg_get_tx_payload_buffer
Error: rpmsgfs/rpmsgfs_client.c:506:7: error: assignment to 'struct rpmsgfs_ioctl_s *' from 'int' makes pointer from integer without a cast [-Werror=int-conversion]
  506 |   msg = rpmsgfs_get_tx_payload_buffer(priv, &space);
      |       ^

Please fix the build

[xiaoxiang781216]

@GUIDINGLI please rebase your patch to fix the ci error