[U-Boot-Users] Revised custodian git writeup

[gvb.uboot]

<http://www.denx.de/wiki/view/UBoot/CustodianGitTrees#Tips_for_maintaining_custodian_t>

I've rewritten the "Tips for maintaining custodian trees" section to 
reflect Wolfgang's request that the "master" branch be used for patches 
for him to pull.

Conceptually, this is very different from my previous recommendation / 
methodology writeup.  In practice, however, it is a trivial change.  The 
fundamental difference is to create a separate branch ("uboot") to track 
the master repo and rebase the "master" branch against that, instead of 
vice versa.

Best regards,
gvb