[IA64] Enable early console for Ski simulator

This patch cleans up the `enable early console for SKI' patch
(471e7a4484), and
1. potentially allows the gensparse_defconfig to work again.
   (there are other problems running a generic kernel on Ski)
2. fixes the `console registered twice' problem.
3. Cleans up the code by moving the `extern hpsim_cons' declaration to
   a new asm/hpsim.h file.

Thanks to Jes for comments.

Signed-off-by: Peter Chubb <peterc@gelato.unsw.edu.au>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-ia64/hpsim.h

@@ -0,0 +1,10 @@
+#ifndef _ASMIA64_HPSIM_H
+#define _ASMIA64_HPSIM_H
+
+#ifndef CONFIG_HP_SIMSERIAL_CONSOLE
+static inline int simcons_register(void) { return 1; }
+#else
+int simcons_register(void);
+#endif
+
+#endif