SF: fix redundant assignment operation.

Bug:none
Test:reboot

Change-Id: I9618284bd99f731bef834e301e4a6bbb94266cfe
Signed-off-by: linkai <linkai@xiaomi.com>
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.cpp b/services/surfaceflinger/DisplayHardware/HWC2.cpp
index aaf2523..8a6a67a 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWC2.cpp
@@ -165,8 +165,7 @@
     auto intError = mComposer.getChangedCompositionTypes(
             mId, &layerIds, &types);
     uint32_t numElements = layerIds.size();
-    auto error = static_cast<Error>(intError);
-    error = static_cast<Error>(intError);
+    const auto error = static_cast<Error>(intError);
     if (error != Error::NONE) {
         return error;
     }