build: Remove "fwdebug" and "common" feature flags

This simplifes the buld and checks with very little overhead and the
fwdebug device is I/O port device on 0x402 that can be used by edk2 as a
very simple character device.

See: #4679

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

Cargo.toml

@@ -54,10 +54,7 @@ test_infra = { path = "test_infra" }
 wait-timeout = "0.2.0"
 
 [features]
-default = ["common", "kvm"]
-# Common features for all hypervisors
-common = ["fwdebug"]
-fwdebug = ["vmm/fwdebug"]
+default = ["kvm"]
 gdb = ["vmm/gdb"]
 guest_debug = ["vmm/guest_debug"]
 kvm = ["vmm/kvm"]