Function pread need macro _XOPEN_SOURCE be defined.
Add _GNU_SOURCE will fix this issue.
error: implicit declaration of function ‘pread’
Fixes: 4a499c6495 ("eal/linux: enable uio_pci_generic support")
Signed-off-by: Marvin Liu <yong.liu@intel.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>