servo_v4: Fix ADC console command

The console adc command prints adc values in the
order they appear in hardware, however they are lableled
in the order they are enumerated in board.h, which is not
necessarily the same.

This prints the correct name and value pairs, and removes
the adc_read_all_channels function which is not otherwise
used.

BUG=chromium:571476
BRANCH=None
TEST="adc" command associates correct values with names now.

Change-Id: I688641953d20082224b4120eaefe0d634ad4c74c
Signed-off-by: Nick Sanders <nsanders@google.com>
Reviewed-on: https://chromium-review.googlesource.com/340892
Commit-Ready: Nick Sanders <nsanders@chromium.org>
Tested-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Shawn N <shawnn@chromium.org>
9 files changed