[rdma-core] Compile issue with DRM headers

[liweihang <liweihang@xxxxxxxxxx>]

Hi Jianxin,

I met a compile error with recent version of rdma-core on my server with Ubuntu
14.04:

./pyverbs/dmabuf_alloc.c:16:24: fatal error: amdgpu_drm.h: No such file or
directory
 #include <amdgpu_drm.h>
                        ^
compilation terminated.

I found it is related with dma-buf based commits. And the commit 3788aa843b4b
("configure: Add check for DRM headers") adds a check for libdrm headers. I have
installed it but my version(2.4.67-1ubuntu0.14.04.2) isn't new enough, there is
no 'amdgpu_drm.h' in DRM_INCLUDE_DIRS(/usr/include/drm).

So I think we may need some check for the the version of libdrm in CMakeList.txt
or something else :) Could you please give me some suggestions?

Thanks
Weihang