doc: releases: Add migration guide to update name for PWM Renesas

Update the naming of Renesas PWM compatible from "renesas,ra8-pwm"
to "renesas,ra-pwm"

Signed-off-by: Khoa Nguyen <[email protected]>

Author: khoa-nguyen-18

doc/releases/migration-guide-4.1.rst

@@ -153,6 +153,11 @@ I2C
 Input
 =====
 
+PWM
+===
+
+* Renamed the ``compatible`` from ``renesas,ra8-pwm`` to :dtcompatible:`renesas,ra-pwm`.
+
 Interrupt Controller
 ====================