xen/arm: move xen_swiotlb_detect to arm/swiotlb-xen.h

Move xen_swiotlb_detect to a static inline function to make it available
to !CONFIG_XEN builds.

CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20210512201823.1963-1-sstabellini@kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>

arch/arm/xen/mm.c

@@ -135,18 +135,6 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
 	return;
 }
 
-int xen_swiotlb_detect(void)
-{
-	if (!xen_domain())
-		return 0;
-	if (xen_feature(XENFEAT_direct_mapped))
-		return 1;
-	/* legacy case */
-	if (!xen_feature(XENFEAT_not_direct_mapped) && xen_initial_domain())
-		return 1;
-	return 0;
-}
-
 static int __init xen_mm_init(void)
 {
 	struct gnttab_cache_flush cflush;

include/xen/arm/swiotlb-xen.h

@@ -2,6 +2,19 @@
 #ifndef _ASM_ARM_SWIOTLB_XEN_H
 #define _ASM_ARM_SWIOTLB_XEN_H
 
-extern int xen_swiotlb_detect(void);
+#include <xen/features.h>
+#include <xen/xen.h>
+
+static inline int xen_swiotlb_detect(void)
+{
+	if (!xen_domain())
+		return 0;
+	if (xen_feature(XENFEAT_direct_mapped))
+		return 1;
+	/* legacy case */
+	if (!xen_feature(XENFEAT_not_direct_mapped) && xen_initial_domain())
+		return 1;
+	return 0;
+}
 
 #endif /* _ASM_ARM_SWIOTLB_XEN_H */