Revert "firmware: stratix10-svc: release mutex sdm_lock after processing command"

This reverts commit 94415527.

The above commit is reverted as deadlock issue was fixed in
7e703d82 ("HSD #16013024105: fpga: stratix10-soc: stop kernel thread").

Signed-off-by: Wentao Zhang <wentao.zhang@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>