kpatch-build: fix ERROR: two parent matches for x.o

We use find_obj to find a target for a .o file. But if a .o file
is like "arch/x86/kvm/../../../virt/kvm/kvm_main.o", we'll got
"ERROR: two parent matches for kvm_main.o"

In this patch, we remove the prefix of the path, ie. changed
"arch/x86/kvm/../../../virt/kvm/kvm_main.o" to "virt/kvm/kvm_main.o"

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
create-diff-object: fix a potential overflow for rela type

rela.type should be unsigned int instead of unsighed char.

/usr/include/gelf.h:#define GELF_R_TYPE(info)   ELF64_R_TYPE (info)
/usr/include/elf.h:#define ELF64_R_TYPE(i)      ((i) & 0xffffffff)

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>