staging:iio:meter: Drop ADE7759 driver

I announced the intent to drop some of these meter drivers
on the IIO list last cycle. This device is obsolete and not easily
obtained.  No one has come forward with suitable test hardware and
the driver would need a lot of work to move out of staging.

As such I am dropping it.  We can always bring it back again
if a user / tester emerges in the future.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/meter/Kconfig

@@ -3,16 +3,6 @@
 #
 menu "Active energy metering IC"
 
-config ADE7759
-	tristate "Analog Devices ADE7759 Active Energy Metering IC Driver"
-	depends on SPI
-	help
-	  Say yes here to build support for Analog Devices ADE7758 Active Energy
-	  Metering IC with di/dt Sensor Interface.
-
-	  To compile this driver as a module, choose M here: the
-	  module will be called ade7759.
-
 config ADE7854
 	tristate "Analog Devices ADE7854/58/68/78 Polyphase Multifunction Energy Metering IC Driver"
 	depends on SPI || I2C

drivers/staging/iio/meter/Makefile

@@ -3,7 +3,6 @@
 # Makefile for metering ic drivers
 #
 
-obj-$(CONFIG_ADE7759) += ade7759.o
 obj-$(CONFIG_ADE7854) += ade7854.o
 obj-$(CONFIG_ADE7854_I2C) += ade7854-i2c.o
 obj-$(CONFIG_ADE7854_SPI) += ade7854-spi.o