powerpc/ftrace: Don't include ftrace.o for CONFIG_FTRACE_SYSCALLS

Since commit 7bea7ac0 ("powerpc/syscalls: Fix syscall tracing")
ftrace.o is not needed anymore for CONFIG_FTRACE_SYSCALLS.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/275932a5d61543b825ff9a64f61abed6da5d4a2a.1652074503.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/trace/Makefile

@@ -17,7 +17,6 @@ endif
 obj-$(CONFIG_FUNCTION_TRACER)		+= ftrace_low.o
 obj-$(CONFIG_DYNAMIC_FTRACE)		+= ftrace.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o
-obj-$(CONFIG_FTRACE_SYSCALLS)		+= ftrace.o
 obj-$(CONFIG_TRACING)			+= trace_clock.o
 
 obj-$(CONFIG_PPC64)			+= $(obj64-y)