servod: Disable ID eeprom access on mimic flex.

Bug in id_eeprom control for the onboard 128Byte EEPROM on mimic
flexes w/ the PCA9500 chip.  As we don't use this EEPROM and the
PCA9500 has been deprecated for future flexes due to leakage issue I'm
removing controls.

Additionally added exceptions if controls are re-added without
addressing the side-effect.

BUG=chromium:294248
TEST=manual
  1. sudo servod -b <board w/ mimic flex>
  2. dut-control spi2_vref:pp1800 spi1_vref:pp1800
  3. dut-control spi2_buf_on_flex_en:off spi1_buf_on_flex_en:off
  3. dut-control | grep spi[12]_buf_on_flex_en

returns
  spi2_buf_on_flex_en:off
  spi1_buf_on_flex_en:off

Change-Id: I094431934bffa648d0682d6ebd30814266a15276
Reviewed-on: https://chromium-review.googlesource.com/169872
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Todd Broch <tbroch@chromium.org>
Tested-by: Todd Broch <tbroch@chromium.org>
3 files changed