pinctrl: nsp: off by ones in nsp_pinmux_enable()

The > comparisons should be >= or else we read beyond the end of the
pinctrl->functions[] array.

Fixes: cc4fa83f ("pinctrl: nsp: add pinmux driver support for Broadcom NSP SoC")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>