livepatch/ppc64: Fix several compilation errors in unwind_frame()

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5CJ7X



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Fix the spelling error of 'CONFIG_ FUNCTION_GRAPH_TRACE' and two
compilation errors:
- 'ftrace_idx' is not defined
- 'struct stackframe' does not have a member named 'ip'

Fixes: ac81d625 ("livepatch/ppc64: Implement livepatch without ftrace for ppc64be")
Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Reviewed-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>