csky: ftrace: Drop duplicate implementation of arch_check_ftrace_location()

The csky specific arch_check_ftrace_location() shadows a weak
implementation of the function in core code that offers the same
functionality but with additional error checking.

Drop the architecture specific function as a step towards further
cleanup in core code.

Link: https://lkml.kernel.org/r/163163034617.489837.7789033031868135258.stgit@devnote2

Signed-off-by: Punit Agrawal <punitagrawal@gmail.com>
Acked-by: Guo Ren <guoren@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>