s390/kasan: sort out physical vs virtual memory confusion

The kasan early boot memory allocators operate on pgalloc_pos
and segment_pos physical address pointers, but fail to convert
it to the corresponding virtual pointers.

Currently it is not a problem, since virtual and physical
addresses on s390 are the same. Nevertheless, should they
ever differ, this would cause an invalid pointer access.
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/mm/kasan_init.c

@@ -39,7 +39,7 @@ static void * __init kasan_early_alloc_segment(void)
 	if (segment_pos < segment_low)
 		kasan_early_panic("out of memory during initialisation\n");
 
-	return (void *)segment_pos;
+	return __va(segment_pos);
 }
 
 static void * __init kasan_early_alloc_pages(unsigned int order)
@@ -49,7 +49,7 @@ static void * __init kasan_early_alloc_pages(unsigned int order)
 	if (pgalloc_pos < pgalloc_low)
 		kasan_early_panic("out of memory during initialisation\n");
 
-	return (void *)pgalloc_pos;
+	return __va(pgalloc_pos);
 }
 
 static void * __init kasan_early_crst_alloc(unsigned long val)