Bump SGX repository to track upstream

Upstream now carries patches to fix compilation problems.

Change-Id: Ie5c6c385e3918b6cf633f3ed89bf3f789b4fe231
Updated Readme with new make targets and links

Change-Id: I4602d32aba0b0f75221d2370d90c92453516dfae
[u-boot] Revert to omap-v2012.10.

v2013.10 causes a problem finding partitions.

Change-Id: I63895f3f57d46960a012aa0dcc7f2fa6873aff4d
[sgx] Use the gumdroid clone for this repository

We are carrying a few extra patches in our branch that haven't been
accepted upstream yet.

Change-Id: Ia656c03fd7c29e70deb2cdaad60e6320707c49a3