csky: Add perf_arch_fetch_caller_regs support

In trace events as tracepoints context are not able to
be retrieve with task_pt_regs. Without arch caller regs
support the pt_regs context will be all zero, perf can
not parsing the callchain and resolving the symbols
correctly, some time will even get into deadlock
while handling the page fault, eg:

perf kmem —page record ls

Changelog
 - Add test case cmd in comment
 - Use regs_fp(regs) which is defined in abi/regdef.h

Signed-off-by: Mao Han <han_mao@c-sky.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

arch/csky/abiv2/inc/abi/regdef.h

@@ -6,6 +6,7 @@
 
 #define syscallid	r7
 #define regs_syscallid(regs) regs->regs[3]
+#define regs_fp(regs) regs->regs[4]
 
 /*
  * PSR format: