sh: syscall: Add missing forward declaration for sys_cacheflush()

arch/sh/kernel/sys_sh.c:58:16: warning: no previous prototype for ‘sys_cacheflush’ [-Wmissing-prototypes]

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: John Paul Adrian Glaubitz <[e-mail]>
Link: https://lore.kernel.org/r/b1c21[e-mail]
Signed-off-by: John Paul Adrian Glaubitz <[e-mail]>

arch/sh/include/asm/syscalls.h

···
 asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
 			  unsigned long prot, unsigned long flags,
 			  unsigned long fd, unsigned long pgoff);
+asmlinkage int sys_cacheflush(unsigned long addr, unsigned long len, int op);
 
 #include <asm/syscalls_32.h>