misc: ti-st: add handling of the signal case

if(!wait_for_completion_interruptible_timeout(...))
only handles the timeout case - this patch adds handling the
signal case the same as timeout.

Only the timeout case was being handled, the signal case
(-ERESTARTSYS) was treated just like the case of successful
completion, which is most likely not reasonable.

read_local_version() is called from download_firmware() where
it checks for !=0 return, so the error handling logic should be
preserved correctly.

download_firmware() is called from st_kim_start() which is
checking for !=0 return, so the error handling logic should be
preserved correctly

Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>