bus: imx-weim: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
switches to using a maximum size and adds a sanity check.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Shawn Guo <shawnguo@kernel.org>

drivers/bus/imx-weim.c

@@ -45,6 +45,8 @@ static const struct imx_weim_devtype imx51_weim_devtype = {
 	.cs_stride	= 0x18,
 };
 
+#define MAX_CS_REGS_COUNT	6
+
 static const struct of_device_id weim_id_table[] = {
 	/* i.MX1/21 */
 	{ .compatible = "fsl,imx1-weim", .data = &imx1_weim_devtype, },
@@ -112,9 +114,12 @@ err:
 static int __init weim_timing_setup(struct device_node *np, void __iomem *base,
 				    const struct imx_weim_devtype *devtype)
 {
-	u32 cs_idx, value[devtype->cs_regs_count];
+	u32 cs_idx, value[MAX_CS_REGS_COUNT];
 	int i, ret;
 
+	if (WARN_ON(devtype->cs_regs_count > MAX_CS_REGS_COUNT))
+		return -EINVAL;
+
 	/* get the CS index from this child node's "reg" property. */
 	ret = of_property_read_u32(np, "reg", &cs_idx);
 	if (ret)