csky: Select ARCH_WANT_FRAME_POINTERS only if compiler supports it

Compiling csky:allmodconfig with an upstream C compiler results
in the following error.

csky-linux-gcc: error:
	unrecognized command-line option '-mbacktrace';
	did you mean '-fbacktrace'?

Select ARCH_WANT_FRAME_POINTERS only if gcc supports it to
avoid the error.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guo Ren <guoren@kernel.org>