[IA64] Fix boot failure on ia64/sn2

Call check_sal_cache_flush() after platform_setup() as
check_sal_cache_flush() now relies on being able to call platform
vector code.

Problem was introduced by: 3463a93def55c309f3c0d0a8aaf216be3be42d64
"Update check_sal_cache_flush to use platform_send_ipi()"

Signed-off-by: Jes Sorensen <[e-mail]>
Tested-by: Alex Chiang: <[e-mail]>
Signed-off-by: Tony Luck <[e-mail]>

arch/ia64/kernel/setup.c

···
 	cpu_init();	/* initialize the bootstrap CPU */
 	mmu_context_init();	/* initialize context_id bitmap */
 
-	check_sal_cache_flush();
-
 #ifdef CONFIG_ACPI
 	acpi_boot_init();
 #endif
···
 		ia64_mca_init();
 
 	platform_setup(cmdline_p);
+	check_sal_cache_flush();
 	paging_init();
 }