package/sane-backends: add patch to fix compile for toolchains without thread support

package/sane-backends: add patch to fix compile for toolchains without thread support

Fixes:

  - http://autobuild.buildroot.net/results/c9b0e41d66211bcab231b5db78c6eebe4b1d78ba

  genesys/scanner_interface_usb.cpp: In member function ‘virtual void genesys::ScannerInterfaceUsb::sleep_us(unsigned int)’:
  genesys/scanner_interface_usb.cpp:484:10: error: ‘std::this_thread’ has not been declared
    484 |     std::this_thread::sleep_for(std::chrono::microseconds{microseconds});
        |          ^~~~

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>