gpio: sx150x: Remove unnecessary MODULE_ALIAS()

The driver has a I2C device id table that is used to create the module
aliases and also "sx150x" isn't a supported I2C id, so it's never used.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>