devices: gpu: conditionally enable capsets if context_mask is specified
devices: gpu: conditionally enable capsets if context_mask is specified

This allows finer grain selection of context types, and eventually deletion
of preprocessor flags and "default component type".

BUG=b:173630595
TEST=compile

Change-Id: I5669911dfd4d6a7fd290e73ed3939d54fabdb89f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3655287
Reviewed-by: Rob Clark <915c10c999604870200b6defbe633d857c856ca0@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm