atv-sdk: use google as brand instead of generic_x86

Current ro.build.fingerprint on oc-release has 92 chars as shown below:
generic_x86/sdk_google_atv_x86/generic_x86:8.0.0/OPR1.170516.001/4012038:userdebug/test-keys
we can shorten it by 5 chars with google brand, similar to other google sdk images
such as sdk_gphone_x86 target.

following is the new fingerprint 87 chars after replacement
google/sdk_google_atv_x86/generic_x86:8.0.0/OPR1.170516.001/4012038:userdebug/test-keys

BUG: 38352731
Change-Id: I938341ac3c11ebe6d966b2cdb14bb2b289ef7ef7
diff --git a/products/sdk_atv_armv7.mk b/products/sdk_atv_armv7.mk
index 45b3d65..2243f4e 100644
--- a/products/sdk_atv_armv7.mk
+++ b/products/sdk_atv_armv7.mk
@@ -70,4 +70,4 @@
 # Overrides
 PRODUCT_NAME := sdk_atv_armv7
 PRODUCT_DEVICE := generic
-PRODUCT_BRAND := generic
+PRODUCT_BRAND := google
diff --git a/products/sdk_atv_x86.mk b/products/sdk_atv_x86.mk
index aa4fb7e..1b6f3f7 100644
--- a/products/sdk_atv_x86.mk
+++ b/products/sdk_atv_x86.mk
@@ -20,4 +20,4 @@
 # Overrides
 PRODUCT_NAME := sdk_atv_x86
 PRODUCT_DEVICE := generic_x86
-PRODUCT_BRAND := generic_x86
+PRODUCT_BRAND := google