xen/vmap: use ISOLATE_LSB to wrap a violation of Rule 10.1

No functional change.

Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/common/vmap.c

@@ -53,7 +53,7 @@ static void *vm_alloc(unsigned int nr, unsigned int align,
     if ( !align )
         align = 1;
     else if ( align & (align - 1) )
-        align &= -align;
+        align = ISOLATE_LSB(align);
 
     ASSERT((t >= VMAP_DEFAULT) && (t < VMAP_REGION_NR));
     if ( !vm_base[t] )