csky: Fixup init_fpu compile warning with __init

WARNING: vmlinux.o(.text+0x2366): Section mismatch in reference from the
function csky_start_secondary() to the function .init.text:init_fpu()

The function csky_start_secondary() references
the function __init init_fpu().
This is often because csky_start_secondary lacks a __init
annotation or the annotation of init_fpu is wrong.

Reported-by: Lu Chongzhi <chongzhi.lcz@alibaba-inc.com>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

arch/csky/kernel/smp.c

@@ -22,6 +22,9 @@
 #include <asm/sections.h>
 #include <asm/mmu_context.h>
 #include <asm/pgalloc.h>
+#ifdef CONFIG_CPU_HAS_FPU
+#include <abi/fpu.h>
+#endif
 
 struct ipi_data_struct {
 	unsigned long bits ____cacheline_aligned;