rog-control-center: Disable slint KMS backend

The slint KMS backend is meant to run an application without a display
server and with direct, exclusive display and input control, which is a
very specific use-case for e.g. embedded applications.

Disable the KMS backend and avoid a bunch of dependencies.

Cargo.lock

@@ -1,6 +1,6 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "ab_glyph"
@@ -2146,7 +2146,6 @@ dependencies = [
  "i-slint-core",
  "i-slint-renderer-femtovg",
  "input",
- "libseat",
  "nix 0.27.1",
  "raw-window-handle",
  "xkbcommon",
@@ -2692,26 +2691,6 @@ dependencies = [
  "redox_syscall 0.5.3",
 ]
 
-[[package]]
-name = "libseat"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "54a0adf8d8607a73a5b74cbe4132f57cb349e4bf860103cd089461bbcbc9907e"
-dependencies = [
- "errno",
- "libseat-sys",
- "log",
-]
-
-[[package]]
-name = "libseat-sys"
-version = "0.1.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3671cb5e03871f1d6bf0b3b5daa9275549e348fa6359e0f9adb910ca163d4c34"
-dependencies = [
- "pkg-config",
-]
-
 [[package]]
 name = "libudev-sys"
 version = "0.1.4"