rusticl/api: remove some repr(C)

The only part we strictly need repr(C) is in `CLObjectBase` and we already
didn't have it set for `Device` and it worked just fine.

We keep it on in `Platform` as this is a more hand rolled type and less
relevant.

With this we can make use of Rusts data layout which saves us some memory.

Signed-off-by: Karol Herbst <git@karolherbst.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23573>

src/gallium/frontends/rusticl/core/event.rs

@@ -33,7 +33,6 @@ struct EventMutState {
     work: Option<EventSig>,
 }
 
-#[repr(C)]
 pub struct Event {
     pub base: CLObjectBase<CL_INVALID_EVENT>,
     pub context: Arc<Context>,

src/gallium/frontends/rusticl/core/kernel.rs

@@ -331,7 +331,6 @@ impl KernelDevState {
     }
 }
 
-#[repr(C)]
 pub struct Kernel {
     pub base: CLObjectBase<CL_INVALID_KERNEL>,
     pub prog: Arc<Program>,

src/gallium/frontends/rusticl/core/memory.rs

@@ -101,7 +101,6 @@ impl Mappings {
     }
 }
 
-#[repr(C)]
 pub struct Mem {
     pub base: CLObjectBase<CL_INVALID_MEM_OBJECT>,
     pub context: Arc<Context>,
@@ -1237,7 +1236,6 @@ impl Drop for Mem {
     }
 }
 
-#[repr(C)]
 pub struct Sampler {
     pub base: CLObjectBase<CL_INVALID_SAMPLER>,
     pub context: Arc<Context>,

src/gallium/frontends/rusticl/core/program.rs

@@ -55,7 +55,6 @@ pub enum ProgramSourceType {
     Il(spirv::SPIRVBin),
 }
 
-#[repr(C)]
 pub struct Program {
     pub base: CLObjectBase<CL_INVALID_PROGRAM>,
     pub context: Arc<Context>,

src/gallium/frontends/rusticl/core/queue.rs

@@ -14,7 +14,6 @@ use std::sync::Mutex;
 use std::thread;
 use std::thread::JoinHandle;
 
-#[repr(C)]
 pub struct Queue {
     pub base: CLObjectBase<CL_INVALID_COMMAND_QUEUE>,
     pub context: Arc<Context>,