selftests/bpf: Fix compilation error in get_uprobe_offset()

In get_uprobe_offset(), the call to procmap_query() use the constant
PROCMAP_QUERY_VMA_EXECUTABLE, even if PROCMAP_QUERY is not defined.

Define PROCMAP_QUERY_VMA_EXECUTABLE when PROCMAP_QUERY isn't.

Fixes: 4e9e0760 ("selftests/bpf: make use of PROCMAP_QUERY ioctl if available")
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20241218175724.578884-1-jmarchan@redhat.com