lib.hardware.pci.map_pci_memory: only wait if first call failed

# Conflicts:
#	src/lib/hardware/pci.lua

src/lib/hardware/pci.lua

@@ -186,17 +186,20 @@ end
 
 function map_pci_memory (f)
    local st = assert(f:stat())
-   local mem
+   local mem, err
+   mem, err = f:mmap(nil, st.size, "read, write", "shared", 0)
    -- mmap() returns EINVAL on Linux >= 4.5 if the device is still
    -- claimed by the kernel driver. We assume that
    -- unbind_device_from_linux() has already been called but it may take
    -- some time for the driver to release the device.
-   lib.waitfor2("mmap of "..filepath,
-                function ()
-                   mem, err = f:mmap(nil, st.size, "read, write", "shared", 0)
-                   assert(not err or err.INVAL)
-                   return mem
-                end, 5, 1000000)
+   if not mem then
+      lib.waitfor2("mmap of "..filepath,
+                   function ()
+                      mem, err = f:mmap(nil, st.size, "read, write", "shared", 0)
+                      assert(not err or err.INVAL)
+                      return mem
+                   end, 5, 1000000)
+   end
    return ffi.cast("uint32_t *", mem)
 end