MIPS: ftrace: Remove redundant #ifdef CONFIG_DYNAMIC_FTRACE

There exists redundant #ifdef CONFIG_DYNAMIC_FTRACE in ftrace.c, remove it.

Signed-off-by: Zejiang Tang <tangzejiang@loongson.cn>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>