leds: lp3952: Export I2C module alias information for module autoload

If the driver is built as a module, I2C module alias information is not
filled so the module won't be autoloaded if the device isn't registered
over ACPI. Export the I2C device table alias with MODULE_DEVICE_TABLE()
macro so the information is exported in the module.

Before this patch:

$ modinfo drivers/leds/leds-lp3952.ko | grep alias
alias:          acpi*:TXNW3952:*

After this patch:

$ modinfo drivers/leds/leds-lp3952.ko | grep alias
alias:          i2c:lp3952
alias:          acpi*:TXNW3952:*

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>