Fix trace file fails on powerpc64

Fix trace file fails on powerpc64

I see the following fails on powerpc64-linux,

(gdb) target tfile tfile-basic.tf^M
warning: Uploaded tracepoint 1 has no source location, using raw address^M
Tracepoint 1 at 0x10012358^M
Created tracepoint 1 for target's tracepoint 1 at 0x10012358.^M
(gdb) PASS: gdb.trace/tfile.exp: target tfile tfile-basic.tf
info trace^M
Num     Type           Disp Enb Address            What^M
1       tracepoint     keep y   0x0000000010012358 <write_basic_trace_file>^M
        installed on target^M
(gdb) FAIL: gdb.trace/tfile.exp: info tracepoints on trace file

-target-select tfile tfile-basic.tf^M
=thread-group-started,id="i1",pid="1"^M
=thread-created,id="1",group-id="i1"^M
&"warning: Uploaded tracepoint 1 has no source location, using raw address\n"^M
=breakpoint-created,bkpt={number="1",type="tracepoint",disp="keep",enabled="y",
addr="0x0000000010012358",at="<write_basic_trace_file>",thread-groups=["i1"],
times="0",installed="y",original-location="*0x10012358"}^M
~"Created tracepoint 1 for target's tracepoint 1 at 0x10012358.\n"^M
^connected^M
(gdb) ^M
FAIL: gdb.trace/mi-traceframe-changed.exp: tfile: select trace file

These fails are caused by writing function descriptor address into trace
file instead of function address.  This patch is to teach tfile.c to
write function address on powerpc64 target.  With this patch applied,
fails in tfile.exp and mi-traceframe-changed.exp are fixed.  Is it
OK?

gdb/testsuite:

2014-10-27  Yao Qi  <yao@codesourcery.com>

	* gdb.trace/tfile.c (adjust_function_address)
	[__powerpc64__ && _CALL_ELF != 2]: Get function address from
	function descriptor.