fix for gcc compile error: variable duplicate define

TBR=harryjin@google.com
BUG=libyuv:529

Review URL: https://codereview.chromium.org/1512793002 .

source/cpu_id.cc

@@ -120,7 +120,6 @@ int GetXCR0() {
 #if (_MSC_FULL_VER >= 160040219)
   xcr0 = (uint32)(_xgetbv(0));  // VS2010 SP1 required.
 #elif defined(__i386__) || defined(__x86_64__)
-  uint32 xcr0 = 0u;
   asm(".byte 0x0f, 0x01, 0xd0" : "=a" (xcr0) : "c" (0) : "%edx");
 #endif  // defined(__i386__) || defined(__x86_64__)
   return xcr0;