get_voltage: return voltage readings in mV

The "Get Measurement" command reports voltage in steps, not in mV:

1.2V, E_VCC, REF+ and REF-:  each step is 5V/4096 (about 1.22mV)
Others: each step is 5V/1024(about 4.88mV)

Change-Id: I2bca951a4e97d21350cb7df3b9e4c596a89a89e7
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/14258
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
1 file changed