powerpc/52xx/mpc52xx_gpt: consolidate chained IRQ handler install/remove

The driver currently sets the handler data and the chained handler in
two separate steps. This creates a theoretical race window where an
interrupt could fire after the handler is set but before the data is
assigned, leading to a NULL pointer dereference.

Replace the two calls with irq_set_chained_handler_and_data() to set
both the handler and its data atomically under the irq_desc->lock.

Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260119061232.889236-1-nichen@iscas.ac.cn

Author: Chen Ni

arch/powerpc/platforms/52xx/mpc52xx_gpt.c

@@ -253,8 +253,7 @@ mpc52xx_gpt_irq_setup(struct mpc52xx_gpt_priv *gpt, struct device_node *node)
 		return;
 	}
 
-	irq_set_handler_data(cascade_virq, gpt);
-	irq_set_chained_handler(cascade_virq, mpc52xx_gpt_irq_cascade);
+	irq_set_chained_handler_and_data(cascade_virq, mpc52xx_gpt_irq_cascade, gpt);
 
 	/* If the GPT is currently disabled, then change it to be in Input
 	 * Capture mode.  If the mode is non-zero, then the pin could be