[IA64] Sanitize assembler code for ia64_sal_os_state

struct ia64_sal_os_state has three semi-independent sections.  The code
in mca_asm.S assumes that these three sections are contiguous, which
makes it very awkward to add new data to this structure.  Remove the
assumption that the sections are contiguous.  Define a macro to shorten
references to offsets in ia64_sal_os_state.

This patch does not change the way that the code behaves.  It just
makes it easier to update the code in future and to add fields to
ia64_sal_os_state when debugging the MCA/INIT handlers.

Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-ia64/mca.h

@@ -69,14 +69,16 @@ typedef struct ia64_mc_info_s {
  */
 
 struct ia64_sal_os_state {
-	/* SAL to OS, must be at offset 0 */
+
+	/* SAL to OS */
 	u64			os_gp;			/* GP of the os registered with the SAL, physical */
 	u64			pal_proc;		/* PAL_PROC entry point, physical */
 	u64			sal_proc;		/* SAL_PROC entry point, physical */
 	u64			rv_rc;			/* MCA - Rendezvous state, INIT - reason code */
 	u64			proc_state_param;	/* from R18 */
 	u64			monarch;		/* 1 for a monarch event, 0 for a slave */
-	/* common, must follow SAL to OS */
+
+	/* common */
 	u64			sal_ra;			/* Return address in SAL, physical */
 	u64			sal_gp;			/* GP of the SAL - physical */
 	pal_min_state_area_t	*pal_min_state;		/* from R17.  physical in asm, virtual in C */
@@ -98,7 +100,8 @@ struct ia64_sal_os_state {
 	u64			iipa;
 	u64			iim;
 	u64			iha;
-	/* OS to SAL, must follow common */
+
+	/* OS to SAL */
 	u64			os_status;		/* OS status to SAL, enum below */
 	u64			context;		/* 0 if return to same context
 							   1 if return to new context */