io: delete gpio for now

I got distracted from this project and left the gpio
package in a bad state. Removing the code for now until
I complete the missing pieces.

Change-Id: I19a21bc83860d98754be2ca59144efb58eb8c535
Reviewed-on: https://go-review.googlesource.com/27351
Reviewed-by: Matt Aimonetti <mattaimonetti@gmail.com>
Reviewed-by: Jaana Burcu Dogan <jbd@google.com>
2 files changed