irqchip/mips-gic: Check the return value of ioremap() in gic_of_init()

The function ioremap() in gic_of_init() can fail, so
its return value should be checked.

Reported-by: Hacash Robot <[e-mail]>
Signed-off-by: William Dean <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/irqchip/irq-mips-gic.c

···
 	}
 
 	mips_gic_base = ioremap(gic_base, gic_len);
+	if (!mips_gic_base) {
+		pr_err("Failed to ioremap gic_base\n");
+		return -ENOMEM;
+	}
 
 	gicconfig = read_gic_config();
 	gic_shared_intrs = FIELD_GET(GIC_CONFIG_NUMINTERRUPTS, gicconfig);