dt-bindings: hwmon: ti,tmp108: document V+ supply, add short description

TMP108 is powered by its V+ supply, document it. The property is called
"vcc-supply" since the plus sign (+) is not an expected character.
While at it, add a short description with a link to its datasheets.

Signed-off-by: Stanislav Jakubek <stano.jakubek@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/ZnBmDXfnDQXNXz3k@standask-GA-A55M-S2HP


Signed-off-by: Guenter Roeck <linux@roeck-us.net>