perf/core: Allow ftrace for functions in kernel/event/core.c

It is useful to trace functions in kernel/event/core.c. Allow ftrace for
them by removing $(CC_FLAGS_FTRACE) from Makefile.

Signed-off-by: Song Liu <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: liu-song-6

kernel/events/Makefile

@@ -1,10 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_FUNCTION_TRACER
-CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE)
-endif
-
 obj-y := core.o ring_buffer.o callchain.o
 
 obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
 obj-$(CONFIG_UPROBES) += uprobes.o
-