scsi: ufs: Clear uic_cmd->cmd_active before calling complete()

Previously, uic_cmd->cmd_active is cleared after completion has been raised
so that we can tell completion timeout happened due to kernel scheduling,
which is for debugging purposes. It is more important, however, to increase
the chance that UIC cmd survives from a completion timeout. So, this change
clears uic_cmd->cmd_active before calling complete().

Change-Id: I99254ac4e3b16dc6b905b5ed5248d53f9c9fc3af
Signed-off-by: Can Guo <cang@codeaurora.org>