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/abiv2/fpu.c

@@ -10,11 +10,6 @@
 #define MTCR_DIST	0xC0006420
 #define MFCR_DIST	0xC0006020
 
-void __init init_fpu(void)
-{
-	mtcr("cr<1, 2>", 0);
-}
-
 /*
  * fpu_libc_helper() is to help libc to excute:
  *  - mfcr %a, cr<1, 2>

arch/csky/abiv2/inc/abi/fpu.h

@@ -9,7 +9,8 @@
 
 int fpu_libc_helper(struct pt_regs *regs);
 void fpu_fpe(struct pt_regs *regs);
-void __init init_fpu(void);
+
+static inline void init_fpu(void) { mtcr("cr<1, 2>", 0); }
 
 void save_to_user_fp(struct user_fp *user_fp);
 void restore_from_user_fp(struct user_fp *user_fp);

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;