sparc32: fix build breakage

Add forward declaration to kernel.h to fix build breakage
in some configurations

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/kernel.h

@@ -27,6 +27,7 @@ static inline unsigned long kimage_addr_to_ra(const char *p)
 
 #ifdef CONFIG_SPARC32
 /* setup_32.c */
+struct linux_romvec;
 void sparc32_start_kernel(struct linux_romvec *rp);
 
 /* cpu.c */