csky: Add support for perf unwind-libdw

This patch add support for DWARF register mappings and libdw registers
initialization, which is used by perf callchain analyzing, eg:

perf record --call-grap

csky: Add support for perf unwind-libdw

This patch add support for DWARF register mappings and libdw registers
initialization, which is used by perf callchain analyzing, eg:

perf record --call-graph=dwarf <COMMAND>

Here is elfutils csky backend patch set:
https://sourceware.org/ml/elfutils-devel/2019-q2/msg00007.html

Signed-off-by: Mao Han <[email protected]>
Signed-off-by: Guo Ren <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Arnd Bergmann <[email protected]>

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