iio: Add t5403 barometric pressure sensor driver

16-bit pressure and temperature sensor

the chip can do I2C and SPI, only the I2C interface is supported
by the driver at the moment

datasheet: http://www.epcos.com/inf/57/ds/T5400.pdf
application note: http://www.epcos.com/blob/993154/download/1/t5403-applicationnote.pdf

an out-of-tree driver targetting the input subsystem is at
https://github.com/unixphere/t5400, it was rejected here:
http://comments.gmane.org/gmane.linux.kernel.input/28107

v2: (thanks Hartmut Knaack)
* fix MODE_HIGH, equals 2
* check INT_TIME mask in write_raw()

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Stefan Nilsson <stefan.nilsson@unixphere.com>
Reviewed-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
index ffac8ac..15afbc9 100644
--- a/drivers/iio/pressure/Kconfig
+++ b/drivers/iio/pressure/Kconfig
@@ -70,4 +70,14 @@
 	depends on IIO_ST_PRESS
 	depends on IIO_ST_SENSORS_SPI
 
+config T5403
+	tristate "EPCOS T5403 digital barometric pressure sensor driver"
+	depends on I2C
+	help
+	  Say yes here to build support for the EPCOS T5403 pressure sensor
+	  connected via I2C.
+
+          To compile this driver as a module, choose M here: the module
+          will be called t5403.
+
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