mips: signal: move sigcontext declarations to header

Function declarations should be in a shared header to ensure the
prototypes match the definition:

arch/mips/kernel/signal.c:439:5: error: no previous prototype for 'setup_sigcontext' [-Werror=missing-prototypes]
arch/mips/kernel/signal.c:516:5: error: no previous prototype for 'restore_sigcontext' [-Werror=missing-prototypes]

Link: https://lkml.kernel.org/r/20231204115710.2247097-6-arnd@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Stephen Rothwell <sfr@rothwell.id.au>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/mips/kernel/signal-common.h

@@ -40,4 +40,7 @@ _restore_fp_context(void __user *fpregs, void __user *csr);
 extern asmlinkage int _save_msa_all_upper(void __user *buf);
 extern asmlinkage int _restore_msa_all_upper(void __user *buf);
 
+extern int setup_sigcontext(struct pt_regs *, struct sigcontext __user *);
+extern int restore_sigcontext(struct pt_regs *, struct sigcontext __user *);
+
 #endif	/* __SIGNAL_COMMON_H */

arch/mips/kernel/signal_n32.c

@@ -33,9 +33,6 @@
  */
 #define __NR_N32_restart_syscall	6214
 
-extern int setup_sigcontext(struct pt_regs *, struct sigcontext __user *);
-extern int restore_sigcontext(struct pt_regs *, struct sigcontext __user *);
-
 struct ucontextn32 {
 	u32		    uc_flags;
 	s32		    uc_link;