riscv: ftrace factor out code defined by !WITH_ARG

DYNAMIC_FTRACE selects DYNAMIC_FTRACE_WITH_ARGS and mcount-dyn.S in
riscv, so we can remove ifdef jargons of WITH_ARG when it is known that
DYNAMIC_FTRACE is true.

Signed-off-by: Andy Chiu <andybnac@gmail.com>
Link: https://lore.kernel.org/r/20250407180838.42877-2-andybnac@gmail.com


Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>