optee: fix tee out of memory failure seen during kexec reboot

optee: fix tee out of memory failure seen during kexec reboot

The following out of memory errors are seen on kexec reboot
from the optee core.

[    0.368428] tee_bnxt_fw optee-clnt0: tee_shm_alloc failed
[    0.368461] tee_bnxt_fw: probe of optee-clnt0 failed with error -22

tee_shm_release() is not invoked on dma shm buffer.

Implement .shutdown() method to handle the release of the buffers
correctly.

More info:
https://github.com/OP-TEE/optee_os/issues/3637

Cc: [email protected]
Signed-off-by: Allen Pais <[email protected]>
Reviewed-by: Tyler Hicks <[email protected]>
Reviewed-by: Jens Wiklander <[email protected]>
Reviewed-by: Sumit Garg <[email protected]>
Signed-off-by: Jens Wiklander <[email protected]>