arm64: configs: Disable ThinLTO for performance impact

Switching from full-LTO to ThinLTO has performance impact on
PtsFirstPartyBenchmarksTestCases:
 - com.google.android.benchmark.pts.BinderPerfBenchmark
 - com.google.android.benchmark.pts.GoogleBenchmarkTest

This patch disable ThinLTO in sunfish_defconfig

Bug: 148617312
Bug: 157708274
Change-Id: I94e6cabac2c7eb0bfe7365ee9ab6b87298eb7920
Signed-off-by: Wilson Sung <wilsonsung@google.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>