libbpf: Add uprobe syscall feature detection

Adding uprobe syscall feature detection that will be used
in following changes.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260224103915.1369690-2-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

src/libbpf_internal.h

@@ -394,6 +394,8 @@ enum kern_feature_id {
 	FEAT_BTF_QMARK_DATASEC,
 	/* Kernel supports LDIMM64 imm offsets past 512 MiB. */
 	FEAT_LDIMM64_FULL_RANGE_OFF,
+	/* Kernel supports uprobe syscall */
+	FEAT_UPROBE_SYSCALL,
 	__FEAT_CNT,
 };