composer: add SKIP_VALIDATE to AIDL

HWC2_CAPABILITY_SKIP_VALIDATE was never defined for HIDL,
and instead there was a hack to just pass the value to the client
(see commit 6a05e9113ab93976fa1e7af9f41aa0af7832b56e).

Test: build
Bug: 198690211
Change-Id: I2b06ad792237eb99e4dfe6b5c1ef808d5de45bd7
3 files changed