u-boot: set SRCREV to a git revision instead of a tag reference
If we use a tag here then bitbake has to connect to the repository to find
out the corresponding revision (so it can expand SRCPV which is part of PV,
which amongst other things is needed to determine whether or not the
package has to be rebuilt.) This occurs at parse time; on machines behind a
firewall or with no network access this can be a problem.
We wish to avoid unnecessary network accesses and network access in our
default configuration during parse time is even worse. Substituting the
git revision corresponding to the tag prevents bitbake from having to
contact the remote repository in order to expand PV.
Addresses [YOCTO #1186]
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
