arm: use the correct prototype for reset_cpu function

Align reset_cpu function with the next prototypes in
sysreset.h or in cpu_func.h to solve compilation issue:

  void reset_cpu(void);

This patch solves the prototype conflict when cpu_func.h is
included.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/board/silinux/ek874/ek874.c b/board/silinux/ek874/ek874.c
index 5a219cd..1e94848 100644
--- a/board/silinux/ek874/ek874.c
+++ b/board/silinux/ek874/ek874.c
@@ -24,7 +24,7 @@
 	return 0;
 }
 
-void reset_cpu(ulong addr)
+void reset_cpu(void)
 {
 	writel(RST_CA53_CODE, RST_CA53RESCNT);
 }