powerpc/ftrace: Don't save again LR in ftrace_regs_caller() on PPC32

PPC32 mcount() caller already saves LR on stack,
no need to save it again.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/eadcfc770b4f1e35535ffb85e28e858a2c31dec4.1640017960.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/trace/ftrace_32.S

@@ -53,9 +53,6 @@ _GLOBAL(ftrace_stub)
 	blr
 
 _GLOBAL(ftrace_regs_caller)
-	/* Save the original return address in A's stack frame */
-	stw	r0,LRSAVE(r1)
-
 	/* Create our stack frame + pt_regs */
 	stwu	r1,-INT_FRAME_SIZE(r1)