iio: pressure: bmp280: add SPI interface driver

This patch mimics the SPI functionality found in the misc driver in
drivers/misc/bh085-spi.c to make it possible to reuse the existing
BMP280/BMP180/BMP085 driver with all clients of the other driver.
The adoption is straight-forward since like the other driver, it is
a simple matter of using regmap.

This driver is also so obviously inspired/copied from the old misc
driver in drivers/misc/bmp085.c that I just took the liberty to
add in the authors of the other drivers + self in the core driver
file.

The MISC driver also supports a variant named "BMP181" so include
that here to be complete in comparison to the old driver.

The bus mapping code for SPI was written by Akinobu Mita.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Tested-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
index f1b5f8c..43bd0b0 100644
--- a/drivers/iio/pressure/bmp280-core.c
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -1,5 +1,9 @@
 /*
+ * Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com>
+ * Copyright (c) 2012 Bosch Sensortec GmbH
+ * Copyright (c) 2012 Unixphere AB
  * Copyright (c) 2014 Intel Corporation
+ * Copyright (c) 2016 Linus Walleij <linus.walleij@linaro.org>
  *
  * Driver for Bosch Sensortec BMP180 and BMP280 digital pressure sensor.
  *