main: restrict the use of vulkan and syncfd flags
main: restrict the use of vulkan and syncfd flags

When using vulkan and syncfd in the gpu parameters with backend
other than gfxstream, crosvm should quit with error messages.

BUG=None
TEST=cargo test --features=gpu,gfxstream

Change-Id: I63c3634598297450ab31f1c1d50c24a0d143e80d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2295841
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Kaiyi Li <f6fa95ef69f95b15c9d6b9a996e5e7cbcfb76e84@google.com>
Auto-Submit: Kaiyi Li <f6fa95ef69f95b15c9d6b9a996e5e7cbcfb76e84@google.com>
Reviewed-by: Zach Reizner <3374927928a53d04457674c546bd4de57c2044ec@chromium.org>

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