pinctrl: spmi-gpio: Use devm_pinctrl_register() for pinctrl registration

Use devm_pinctrl_register() for pin control registration and clean
the error path.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Cc: "Björn Andersson" <bjorn.andersson@sonymobile.com>
Cc: "Ivan T. Ivanov" <ivan.ivanov@linaro.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Jonas Gorski <jogo@openwrt.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>