rust: pwm: Add module_pwm_platform_driver! macro

Rust PWM drivers using the abstractions in `kernel/pwm.rs` typically
call C functions (like `pwmchip_alloc`, `__pwmchip_add`, etc.) that are
exported to the `PWM` C symbol namespace.

With the introduction of `imports_ns` support in the `module!` macro,
every PWM driver would need to manually include `imports_ns: ["PWM"]` in
its module declaration.

To simplify this for driver authors and ensure consistency, introduce a
new helper macro `module_pwm_platform_driver!` in `pwm.rs`. This macro
wraps the standard `module_platform_driver!`, forwards all user provided
arguments using the `($($user_args:tt)*)` pattern, and automatically
injects the `imports_ns: ["PWM"]` declaration.

This follows the pattern used in other subsystems (e.g.,
`module_pci_driver!`) to provide specialized module registration
helpers. It makes writing PWM drivers slightly simpler and less error
prone regarding namespace imports.

Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev>
Link: https://patch.msgid.link/20251028-pwm_fixes-v1-2-25a532d31998@samsung.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

Author: Michal Wilczynski

rust/kernel/pwm.rs

@@ -760,3 +760,26 @@ impl<T: PwmOps> Drop for Registration<T> {
         unsafe { bindings::pwmchip_remove(chip_raw); }
     }
 }
+
+/// Declares a kernel module that exposes a single PWM driver.
+///
+/// # Examples
+///
+///```ignore
+/// kernel::module_pwm_platform_driver! {
+///     type: MyDriver,
+///     name: "Module name",
+///     authors: ["Author name"],
+///     description: "Description",
+///     license: "GPL v2",
+/// }
+///```
+#[macro_export]
+macro_rules! module_pwm_platform_driver {
+    ($($user_args:tt)*) => {
+        $crate::module_platform_driver! {
+            $($user_args)*
+            imports_ns: ["PWM"],
+        }
+    };
+}