libdrm: fix libatomic_ops linking

libdrm: fix libatomic_ops linking

Add patch 0003-configure-Makefile.am-use-pkg-config-to-discover-lib.patch
provided by Thomas Petazzoni handling libatomic_ops linking when needed.

Fixes [1]:

    CCLD     etnaviv_cmd_stream_test
  ../../etnaviv/.libs/libdrm_etnaviv.so: undefined reference to `AO_store_full_emulation'
  ../../etnaviv/.libs/libdrm_etnaviv.so: undefined reference to `AO_fetch_compare_and_swap_emulation'
  collect2: error: ld returned 1 exit status

[1] http://autobuild.buildroot.net/results/92e074c49417261843eef95872ff935a56077c98

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