Revert "CHROMIUM: Use IS_ENABLED(CONFIG_ARM64) as the guard"

This reverts commit 1123b84d.

This actually causes a build error. I guess the code actually doesn't
work in our branch, but because we were only building for x86, it was
fine as we didn't go into the #ifdef.

Bug: 267783246
Test: SKIP_MRPROPER=1 BUILD_CONFIG=common/build.config.gki.x86_64 build/build.sh -j

Change-Id: I79bd25d790adf8638892ebe04297a8428f5c018c
Signed-off-by: Richard Fung <richardfung@google.com>