riscv: Stop supporting static ftrace

Now that DYNAMIC_FTRACE was introduced, there is no need to support
static ftrace as it is way less performant. This simplifies the code and
prevents build failures as reported by kernel test robot when
!DYNAMIC_FTRACE.

Also make sure that FUNCTION_TRACER can only be selected if
DYNAMIC_FTRACE is supported (we have a dependency on the toolchain).

Co-developed-by: chenmiao <chenmiao.ku@gmail.com>
Signed-off-by: chenmiao <chenmiao.ku@gmail.com>
Fixes: b2137c3 ("riscv: ftrace: prepare ftrace for atomic code patching")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506191949.o3SMu8Zn-lkp@intel.com/
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250716-dev-alex-static_ftrace-v1-1-ba5d2b6fc9c0@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>

Author: Alexandre Ghiti

arch/riscv/Kconfig

@@ -98,6 +98,7 @@ config RISCV
 	select CLONE_BACKWARDS
 	select COMMON_CLK
 	select CPU_PM if CPU_IDLE || HIBERNATION || SUSPEND
+	select DYNAMIC_FTRACE if FUNCTION_TRACER
 	select EDAC_SUPPORT
 	select FRAME_POINTER if PERF_EVENTS || (FUNCTION_TRACER && !DYNAMIC_FTRACE)
 	select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY if DYNAMIC_FTRACE
@@ -162,7 +163,7 @@ config RISCV
 	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
 	select HAVE_FUNCTION_GRAPH_TRACER if HAVE_DYNAMIC_FTRACE_WITH_ARGS
 	select HAVE_FUNCTION_GRAPH_FREGS
-	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
+	select HAVE_FUNCTION_TRACER if !XIP_KERNEL && HAVE_DYNAMIC_FTRACE
 	select HAVE_EBPF_JIT if MMU
 	select HAVE_GUP_FAST if MMU
 	select HAVE_FUNCTION_ARG_ACCESS_API