Merge branch 'samples/bpf: xdpsock: Minor enhancements'

Simon Horman says:

====================
This short series provides minor enhancements to the
sample code in samples/bpf/xdpsock_user.c.

Each change is explained more fully in its own commit message.
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>