android: use more basic CPU target for memtag

This is required for hardened_malloc to work in microdroid on MTE-enabled devices (currently, 8th
and 9th generation Pixels) since PVMFW only supports ARMv8 cores.

https://android.googlesource.com/platform/packages/modules/Virtualization/+/refs/tags/android-15.0.0_r1/pvmfw/platform.dts#100

Android.bp

@@ -74,7 +74,7 @@ cc_library {
             cflags: ["-DLABEL_MEMORY"],
         },
         device_has_arm_mte: {
-            cflags: ["-DHAS_ARM_MTE", "-march=armv9-a+memtag"]
+            cflags: ["-DHAS_ARM_MTE", "-march=armv8-a+dotprod+memtag"]
         },
     },
     apex_available: [