iio: light: bh1750: Resolve compiler warning and make code more readable

Separate the declaration of struct bh1750_chip_info from definition
of bh1750_chip_info_tbl[] in a single statement as it makes the code
hard to read, and with the extra newline it makes it look as if the
bh1750_chip_info_tbl[] had no explicit type.

This change also resolves the following compiler warning about the
unusual position of the static keyword that can be seen when building
with warnings enabled (W=1):

drivers/iio/light/bh1750.c:64:1: warning:
  ‘static’ is not at beginning of declaration [-Wold-style-declaration]

Related to commit 3a11fbb0 ("iio: light: add support for ROHM
BH1710/BH1715/BH1721/BH1750/BH1751 ambient light sensors").

Signed-off-by: Krzysztof Wilczynski <kw@linux.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>