ANDROID: cuttlefish_defconfig: Enable CONFIG_RTC_HCTOSYS

This configuration is required for the VTS test
VtsKernelApiSysfsTest#testRtcHctosys to pass.

Bug: 123860857
Test: run vts-kernel -m VtsKernelApiSysfsTest
Signed-off-by: Matthias Maennich <maennich@google.com>
Change-Id: Icae17c74460bcd2aef4cf4e3ec5381de9ea0a66c