Set TARGET_2ND_ARCH_VARIANT to armv8-a

Taimen and Walleye are armv8 devices. Setting TARGET_2ND_ARCH_VARIANT
to armv8-a, instead of armv7-a-neon, can silence the related warning
during build.

Bug: 68012286
Test: lunch aosp_taimen; make -j
      lunch aosp_walleye; make -j

Change-Id: I9c81e614a7f103cd93c9c2d915d53577e8d19d2d
Merged-In: I9c81e614a7f103cd93c9c2d915d53577e8d19d2d
(cherry picked from commit 2195c105e561a78415e965bbe7a34c49dbf941db)
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 4085bb5..0387dae 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -23,7 +23,7 @@
 TARGET_CPU_VARIANT := cortex-a73
 
 TARGET_2ND_ARCH := arm
-TARGET_2ND_ARCH_VARIANT := armv7-a-neon
+TARGET_2ND_ARCH_VARIANT := armv8-a
 TARGET_2ND_CPU_ABI := armeabi-v7a
 TARGET_2ND_CPU_ABI2 := armeabi
 TARGET_2ND_CPU_VARIANT := cortex-a73