nak/bindings: Use an enum for IOCTL numbers

This should be more robust against weird bindgen shenanigans because it
forces LLVM to constant-fold and give us an actual thing we can generate
bindings for.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/12008
Fixes: cd7128c2e3 ("nak: Add a bare HW shader runner")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31727>

src/nouveau/compiler/nak/hw_runner.rs

@@ -190,7 +190,7 @@ impl<'a> Runner {
             };
             let err = drmIoctl(
                 self.dev.as_ref().fd,
-                DRM_RS_IOCTL_NOUVEAU_EXEC,
+                DRM_RS_IOCTL_NOUVEAU_EXEC.into(),
                 &exec as *const _ as *mut std::os::raw::c_void,
             );
             if err != 0 {
@@ -226,7 +226,7 @@ impl<'a> Runner {
             };
             let err = drmIoctl(
                 self.dev.as_ref().fd,
-                DRM_RS_IOCTL_NOUVEAU_EXEC,
+                DRM_RS_IOCTL_NOUVEAU_EXEC.into(),
                 ptr::from_mut(&mut exec).cast(),
             );
             if err != 0 {

src/nouveau/compiler/nak_bindings.h

@@ -13,6 +13,8 @@
 #include "drm-uapi/nouveau_drm.h"
 
 #define DRM_RS_IOCTL(FOO) \
-   static const unsigned long DRM_RS_IOCTL_##FOO = DRM_IOCTL_##FOO
+   DRM_RS_IOCTL_##FOO = DRM_IOCTL_##FOO
 
-DRM_RS_IOCTL(NOUVEAU_EXEC);
+enum ENUM_PACKED drm_rs_ioctls {
+   DRM_RS_IOCTL(NOUVEAU_EXEC),
+};