libbpf: fix -Wformat warnings from format/argument type mismatches

Building libbpf with -Wall (as happens via bpftool's bootstrap build)
surfaces ~120 -Wformat warnings where pr_warn/pr_debug format specifiers
don't match their argument types: %d for __u32/Elf64_Word, %u for signed
ints, %zd for size_t, %ld for unsigned long, and %x/%lx/%llx applied to
signed values.

Match each specifier to its argument's type where a correctly-signed
specifier exists (%d<->%u, %ld->%lu, %zd->%zu). For hex conversions,
which have no signed form, cast the argument instead (%x->(unsigned),
%lx->(unsigned long), %llx->(unsigned long long)). No functional change.

Note, the fdinfo map_flags sscanf used %i into a __u32 *, which warns.
The kernel prints map_flags as hex ("map_flags:\t%#x\n" in
bpf_map_show_fdinfo(), unchanged since the field was added to fdinfo), so
switch the conversion to %x: it parses the 0x-prefixed value and expects
unsigned int *, matching the destination, so the warning is gone with no
cast.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20260624204946.2901178-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

src/elf.c

@@ -354,7 +354,7 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
 
 	if (ret > 0) {
 		pr_debug("elf: symbol address match for '%s' in '%s': 0x%lx\n", name, binary_path,
-			 ret);
+			 (unsigned long)ret);
 	} else {
 		if (ret == 0) {
 			pr_warn("elf: '%s' is 0 in symtab for '%s': %s\n", name, binary_path,