sparc64: fix sparse "Should it be static?" warnings in signal32.c

Fix following warnings:
signal32.c:140:6: warning: symbol 'do_sigreturn32' was not declared. Should it be static?
signal32.c:230:17: warning: symbol 'do_rt_sigreturn32' was not declared. Should it be static?
signal32.c:729:6: warning: symbol 'do_signal32' was not declared. Should it be static?
signal32.c:773:16: warning: symbol 'do_sys32_sigstack' was not declared. Should it be static?

Add proper prototypes and drop local prototype

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc/kernel/kernel.h b/arch/sparc/kernel/kernel.h
index eeb87f7..980e21d 100644
--- a/arch/sparc/kernel/kernel.h
+++ b/arch/sparc/kernel/kernel.h
@@ -44,6 +44,12 @@
 /* pci.c */
 int pci64_dma_supported(struct pci_dev *pdev, u64 device_mask);
 
+/* signal32.c */
+void do_sigreturn32(struct pt_regs *regs);
+asmlinkage void do_rt_sigreturn32(struct pt_regs *regs);
+void do_signal32(struct pt_regs * regs);
+asmlinkage int do_sys32_sigstack(u32 u_ssptr, u32 u_ossptr, unsigned long sp);
+
 #endif
 
 #ifdef CONFIG_SPARC32