powerpc/ftrace: Move stack setup and teardown code into ftrace_graph_caller()

Move the stack setup and teardown code into ftrace_graph_caller(). This way, we
don't incur the cost of setting it up unless function graph is enabled for this
function.

Also, remove the extraneous LR restore code after the function graph stub. LR
has previously been restored and neither livepatch_handler() nor
ftrace_graph_caller() return back here.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
[mpe: Drop bad change to non-mprofile-kernel version of ftrace_graph_caller]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/entry_64.S

@@ -1313,16 +1313,12 @@ ftrace_call:
 #endif
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-	stdu	r1, -112(r1)
 .globl ftrace_graph_call
 ftrace_graph_call:
 	b	ftrace_graph_stub
 _GLOBAL(ftrace_graph_stub)
-	addi	r1, r1, 112
 #endif
 
-	ld	r0,LRSAVE(r1)	/* restore callee's lr at _mcount site */
-	mtlr	r0
 	bctr			/* jump after _mcount site */
 #endif /* CC_USING_MPROFILE_KERNEL */
 
@@ -1471,6 +1467,7 @@ _GLOBAL(ftrace_graph_caller)
 
 #else /* CC_USING_MPROFILE_KERNEL */
 _GLOBAL(ftrace_graph_caller)
+	stdu	r1, -112(r1)
 	/* with -mprofile-kernel, parameter regs are still alive at _mcount */
 	std	r10, 104(r1)
 	std	r9, 96(r1)