drivers:misc: ti-st: reinit completion on ver read

After the version information has been read, the completion which assists in
wait_for_completion during the firmware send/wait sequence is being re-used
and hence this needs to be re-initialised for fool proof firmware download
retries.

Signed-off-by: Pavan Savoy <pavan_savoy@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>