objdump: fix print formatters for 64-bit integers

Commit 071f8a902eb29d29b9306b1425392e9fc73470f3 added support for
dumping BTF info with objdump.  But it used non-portable formatting
directives for some 64-bit integer values, which breaks on some
targets.  Use portable print formatters.

Signed-off-by: David Faust <david.faust@oss.qualcomm.com>