irqchip/imx-intmux: Annotate struct intmux_data with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct intmux_data.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Thomas Gleixner <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Shawn Guo <[email protected]>
Cc: Sascha Hauer <[email protected]>
Cc: Pengutronix Kernel Team <[email protected]>
Cc: Fabio Estevam <[email protected]>
Cc: NXP Linux Team <[email protected]>
Cc: [email protected]
Reviewed-by: "Gustavo A. R. Silva" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Kees Cook <[email protected]>

Author: kees

drivers/irqchip/irq-imx-intmux.c

@@ -73,7 +73,7 @@ struct intmux_data {
 	void __iomem			*regs;
 	struct clk			*ipg_clk;
 	int				channum;
-	struct intmux_irqchip_data	irqchip_data[];
+	struct intmux_irqchip_data	irqchip_data[] __counted_by(channum);
 };
 
 static void imx_intmux_irq_mask(struct irq_data *d)