gpio: davinci: Fix possible NULL pointer deference

This fixes a possible NULL pointer deference in the function,
davinci_gpio_probe due to the function, gpio2regs being able
to return a NULL pointer if it rans to get the registers for
the gpio devices on a davinci board. Furthermore if this does
arise return -ENXIO to signal callers that this case has arisen
and avoiding setting the regs or other pointer values on the
Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-davinci.c

@@ -257,6 +257,8 @@ static int davinci_gpio_probe(struct platform_device *pdev)
 		spin_lock_init(&chips[i].lock);
 
 		regs = gpio2regs(base);
+		if (!regs)
+			return -ENXIO;
 		chips[i].regs = regs;
 		chips[i].set_data = &regs->set_data;
 		chips[i].clr_data = &regs->clr_data;