twister: add fixtures given by --fixture option to each devices.

fixtures could also be given by twister command with --fixture option
explicitly, not only hardware map file. In this case, we should
assign those fixtures to each devices too.

Signed-off-by: Chen Peng1 <peng1.chen@intel.com>

scripts/twister

@@ -990,6 +990,11 @@ def main():
                              --device-serial or --device-serial-pty,
                              only one platform is allowed""")
 
+    # the fixtures given by twister command explicitly should be assigned to each DUTs
+    if suite.fixtures:
+        for d in suite.duts:
+            d.fixtures.extend(suite.fixtures)
+
     if suite.load_errors:
         sys.exit(1)