Add cortex-a73 support.

Also, update flags for cortex-a53.

Bug: 37647380

Test: Built target with cortex-a73 for both 32 bit/64 bit.
Test: Built target with cortex-a53.cortex-a57 for both 32 bit/64 bit.
Test: Ran bionic unit tests, ran art target tests.

(cherry picked from commit 1d9aa26d44)

Change-Id: I3325f60add7f424f8cca53c22919fc481ef5e787

cc/config/arm64_device.go

@@ -93,7 +93,8 @@ const (
 func init() {
 	android.RegisterArchVariants(android.Arm64,
 		"armv8_a",
-		"cortex_a53",
+		"cortex-a53",
+		"cortex-a73",
 		"kryo",
 		"denver64")
 
@@ -129,12 +130,14 @@ var (
 	arm64CpuVariantCflagsVar = map[string]string{
 		"":           "",
 		"cortex-a53": "${config.Arm64CortexA53Cflags}",
+		"cortex-a73": "${config.Arm64CortexA53Cflags}",
 		"kryo":       "${config.Arm64KryoCflags}",
 	}
 
 	arm64ClangCpuVariantCflagsVar = map[string]string{
 		"":           "",
 		"cortex-a53": "${config.Arm64ClangCortexA53Cflags}",
+		"cortex-a73": "${config.Arm64ClangCortexA53Cflags}",
 		"kryo":       "${config.Arm64ClangKryoCflags}",
 	}
 )