scripts/faddr2line: Fix vmlinux detection on arm64

Since commit dcea997b ("faddr2line: Fix overlapping text section
failures, the sequel"), faddr2line is completely broken on arm64.

For some reason, on arm64, the vmlinux ELF object file type is ET_DYN
rather than ET_EXEC.  Check for both when determining whether the object
is vmlinux.

Modules and vmlinux.o have type ET_REL on all arches.

Fixes: dcea997b ("faddr2line: Fix overlapping text section failures, the sequel")
Reported-by: John Garry <john.garry@huawei.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/dad1999737471b06d6188ce4cdb11329aa41682c.1658426357.git.jpoimboe@kernel.org