package/dpdk: fix example build issue when libvirt is present

When libvirt is present before DPDK is built, some additional examples
are compiled. One of them fails to build due to a missing <stdlib.h>
include. Let's import a patch from OpenSuse, that we have submitted
upstream, to fix this issue.

We couldn't find any autobuilder failure for this issue, but the
following defconfig allows to reproduce the failure:

BR2_aarch64=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_AARCH64_GLIBC_STABLE=y
BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
BR2_PACKAGE_DPDK=y
BR2_PACKAGE_DPDK_EXAMPLES=y
BR2_PACKAGE_LIBVIRT=y

The problem exists since DPDK v19.11, so it has been in Buildroot
since DPDK was introduced in commit
d17d1b6bde95d46376c4fe93e8ca1a1f9da6c179.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>