imx6: add driver for temp/voltage monitoring

The Gateworks System Controller (GSC) mimics a standard AD7418 device on
I2C bus 0 at slave 0x29.

Signed-off-by: Koen Vandeputte <koen.vandeputte@ncentric.com>

target/linux/imx6/config-4.9

@@ -263,6 +263,7 @@ CONFIG_HAVE_SMP=y
 CONFIG_HAVE_SYSCALL_TRACEPOINTS=y
 CONFIG_HAVE_UID16=y
 CONFIG_HAVE_VIRT_CPU_ACCOUNTING_GEN=y
+CONFIG_HWMON=y
 CONFIG_HW_RANDOM=y
 CONFIG_HZ_FIXED=0
 CONFIG_HZ_PERIODIC=y
@@ -323,6 +324,7 @@ CONFIG_MXS_DMA=y
 CONFIG_NEED_DMA_MAP_STATE=y
 CONFIG_NEON=y
 CONFIG_NET_DSA=y
+CONFIG_NET_DSA_HWMON=y
 CONFIG_NET_DSA_MV88E6XXX=y
 CONFIG_NET_DSA_MV88E6XXX_GLOBAL2=y
 CONFIG_NET_DSA_TAG_DSA=y
@@ -416,6 +418,7 @@ CONFIG_RWSEM_SPIN_ON_OWNER=y
 CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 # CONFIG_SCHED_INFO is not set
 CONFIG_SCSI=y
+CONFIG_SENSORS_AD7418=y
 CONFIG_SERIAL_8250_FSL=y
 CONFIG_SERIAL_IMX=y
 CONFIG_SERIAL_IMX_CONSOLE=y