rambi: memory: Add support for variable number of RAM_ID GPIOs

Rambi initially supported only three RAM_ID GPIOs, but we have added a
fourth GPIO for upcoming builds. Build the SPD index based upon the
platform-specified number of GPIOs (currently 3 for all but Glimmer, but
this will change later).

TEST=Manual on Rambi. Verify SPD index 3 is correctly probed before and
after change.

Change-Id: I12d4ab38c06311cbb74968f6df5f60e831a341b1
Reviewed-on: https://chromium-review.googlesource.com/187182
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Tested-by: Shawn Nematbakhsh <shawnn@chromium.org>
Commit-Queue: Shawn Nematbakhsh <shawnn@chromium.org>
1 file changed