misc: bh1780: probe from compatible string

Currently the BH1780GLI I2C driver relies on the device tree node
having the right name, but this is fragile. Use the compatible
string to probe the driver instead.

Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>