libraw1394: add patch to fix CLOCK_MONOTONIC_RAW build problem

CLOCK_MONOTONIC_RAW is a fairly recent addition, which may not be
available in old C libraries/kernels. This commit adds a libraw1394
patch that makes the use of CLOCK_MONOTONIC_RAW optional. The patch
has been submitted upstream.

Fixes:

  http://autobuild.buildroot.net/results/198149e80be3e62eaf9f4731442031a1aa93409c/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>