MIPS: RB532: Fix iomap resource size miscalculation.

This is the MIPS portion of Joe Perches <joe@perches.com>'s
https://patchwork.linux-mips.org/patch/2172/ which seems to have been
lost in time and space.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/rb532/gpio.c

@@ -185,7 +185,7 @@ int __init rb532_gpio_init(void)
 	struct resource *r;
 
 	r = rb532_gpio_reg0_res;
-	rb532_gpio_chip->regbase = ioremap_nocache(r->start, r->end - r->start);
+	rb532_gpio_chip->regbase = ioremap_nocache(r->start, resource_size(r));
 
 	if (!rb532_gpio_chip->regbase) {
 		printk(KERN_ERR "rb532: cannot remap GPIO register 0\n");