[PARISC] Fix kernel panic in check_ivt

check_ivt had some seriously broken code wrt function pointers on
parisc64. Instead of referencing the hpmc code via a function pointer,
export symbols and reference it as a const array.

Thanks to jda for pointing out the broken 64-bit func ptr handling.
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

arch/parisc/kernel/hpmc.S

@@ -295,8 +295,5 @@ os_hpmc_6:
 	b .
 	nop
 ENDPROC(os_hpmc)
-
-	/* this label used to compute os_hpmc checksum */
-ENTRY(os_hpmc_end)
-
+ENTRY(os_hpmc_end)	/* this label used to compute os_hpmc checksum */
 	nop

arch/parisc/kernel/traps.c

@@ -802,13 +802,14 @@ void handle_interruption(int code, struct pt_regs *regs)
 
 int __init check_ivt(void *iva)
 {
+	extern const u32 os_hpmc[];
+	extern const u32 os_hpmc_end[];
+
 	int i;
 	u32 check = 0;
 	u32 *ivap;
 	u32 *hpmcp;
 	u32 length;
-	extern void os_hpmc(void);
-	extern void os_hpmc_end(void);
 
 	if (strcmp((char *)iva, "cows can fly"))
 		return -1;
@@ -820,7 +821,7 @@ int __init check_ivt(void *iva)
 
 	/* Compute Checksum for HPMC handler */
 
-	length = (u32)((unsigned long)os_hpmc_end - (unsigned long)os_hpmc);
+	length = os_hpmc_end - os_hpmc;
 	ivap[7] = length;
 
 	hpmcp = (u32 *)os_hpmc;