drivers: gpio: msm: Fix the error condition for reading ngpio

of_property_read_u32 return 0 on success. The check was using a ! to
return error. Fix the if condition.

Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Pankaj Jangra <jangra.pankaj9@gmail.com>
Cc: "Bird, Tim" <Tim.Bird@sonymobile.com>
Signed-off-by: David Brown <davidb@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>