ioctl: Use raw opcodes to match kernel definitions

Replace rustix ioctl macros with hardcoded values for LOOP_CTL_GET_FREE
and LOOP_CONFIGURE. The macro-generated opcodes don't match the kernel's
expected values, causing EINVAL errors. The older kernels (even new ones
6.18 for that matter) define these as raw numbers rather than following
the modern _IOW/_IOR conventions

I have tested this on Fedora 42 (6.18), and CI failure occured on Ubuntu
22.04. I won't if this is distro related and if different distros have
different headers

Signed-off-by: Pragyan Poudyal <pragyanpoudyal41999@gmail.com>

Author: Johan-Liebert1

crates/composefs-ioctls/src/loop_device.rs

@@ -11,7 +11,7 @@ use std::{
     os::fd::{AsFd, AsRawFd, OwnedFd},
 };
 
-use rustix::ioctl::{ioctl, opcode, Opcode, Setter};
+use rustix::ioctl::{ioctl, Opcode, Setter};
 
 /// Flags for loop device configuration.
 pub mod flags {
@@ -102,9 +102,9 @@ unsafe impl rustix::ioctl::Ioctl for LoopCtlGetFree {
     }
 }
 
-const LOOP_CTL_GET_FREE: Opcode = opcode::none(0x4C, 0x82);
+const LOOP_CTL_GET_FREE: Opcode = 0x4C82;
 // #define LOOP_CONFIGURE         0x4C0A
-const LOOP_CONFIGURE: Opcode = opcode::write::<LoopConfig>(0x4C, 0x0A);
+const LOOP_CONFIGURE: Opcode = 0x4C0A;
 
 /// Creates a loop device backed by the given file.
 ///