dfu: Reset timeout in case of DFU request

In case dfu command is being executed with timeout option,
the timer may expire in the middle of DFU operation. If there
is DFU request coming, we may simple reset timeout value
to prevent aborting of ongoing DFU operation.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Ferry Toth <ftoth@exalondelft.nl>