rust: pwm: Add __rust_helper to helpers

This is needed to inline these helpers into Rust code.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Michal Wilczynski <m.wilczynski@samsung.com>
Link: https://patch.msgid.link/20260105-define-rust-helper-v2-14-51da5f454a67@google.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

Author: Darksonn

rust/helpers/pwm.c

@@ -4,17 +4,17 @@
 
 #include <linux/pwm.h>
 
-struct device *rust_helper_pwmchip_parent(const struct pwm_chip *chip)
+__rust_helper struct device *rust_helper_pwmchip_parent(const struct pwm_chip *chip)
 {
 	return pwmchip_parent(chip);
 }
 
-void *rust_helper_pwmchip_get_drvdata(struct pwm_chip *chip)
+__rust_helper void *rust_helper_pwmchip_get_drvdata(struct pwm_chip *chip)
 {
 	return pwmchip_get_drvdata(chip);
 }
 
-void rust_helper_pwmchip_set_drvdata(struct pwm_chip *chip, void *data)
+__rust_helper void rust_helper_pwmchip_set_drvdata(struct pwm_chip *chip, void *data)
 {
 	pwmchip_set_drvdata(chip, data);
 }