Added suffix libdrm to CMakeLists.txt for drm

Cannonical libdrm package installation results in headers installed at
`\usr\include\libdrm`. The current CMakeLists.txt installation script
search the headers only in `drm` suffix which is where headers are found
in readhat base distros. I propose to add also the cannonical path
`libdrm` also used in distros like archlinux.

Signed-off-by: Hector Martinez-Seara <hseara@gmail.com>

CMakeLists.txt

@@ -539,7 +539,7 @@ RDMA_DoFixup("${SYSTEMD_FOUND}" "systemd/sd-daemon.h")
 # drm headers
 
 # Check if the headers have been installed by kernel-headers
-find_path(DRM_INCLUDE_DIRS "drm.h" PATH_SUFFIXES "drm")
+find_path(DRM_INCLUDE_DIRS "drm.h" PATH_SUFFIXES "drm" "libdrm")
 
 # Alternatively the headers could have been installed by libdrm
 if (NOT DRM_INCLUDE_DIRS)