[wlan][iwlwifi] minor refactoring of dependency of testing cases.

BUG=WLAN-1129
TEST=Build successfully.

Change-Id: I1aa2712f3c821f0c6a5b9150e248a3dc862e2aed
diff --git a/src/connectivity/wlan/drivers/third_party/intel/iwlwifi/test/BUILD.gn b/src/connectivity/wlan/drivers/third_party/intel/iwlwifi/test/BUILD.gn
index 41373e9..83d84bd5 100644
--- a/src/connectivity/wlan/drivers/third_party/intel/iwlwifi/test/BUILD.gn
+++ b/src/connectivity/wlan/drivers/third_party/intel/iwlwifi/test/BUILD.gn
@@ -22,6 +22,11 @@
   ]
 }
 
+testing_deps = [
+  "//src/connectivity/wlan/drivers/third_party/intel/iwlwifi:iwlwifi_sim_trans_ss",
+  "//src/lib/fxl/test:gtest_main",
+]
+
 executable("dummy_test") {
   output_name = "dummy_test"
   testonly = true
@@ -30,10 +35,7 @@
     "dummy_test.cc",
   ]
 
-  deps = [
-    "//src/connectivity/wlan/drivers/third_party/intel/iwlwifi:iwlwifi_sim_trans_ss",
-    "//src/lib/fxl/test:gtest_main",
-  ]
+  deps = testing_deps
 }
 
 executable("utils_test") {
@@ -44,10 +46,7 @@
     "utils_test.cc",
   ]
 
-  deps = [
-    "//src/connectivity/wlan/drivers/third_party/intel/iwlwifi:iwlwifi_sim_trans_ss",
-    "//src/lib/fxl/test:gtest_main",
-  ]
+  deps = testing_deps
 }
 
 package("iwlwifi_test") {