create-pull-request: generalize the repository URL parsing

create-pull-request: generalize the repository URL parsing

The existing REMOTE_URL and REMOTE_REPO parsing made assumptions regarding
the git URL format used for the known repository types. In fact, both of
these ssh URL formats are valid for all the known repositories. Specifically:

  ssh://git@server/repository/path
  git@server:repository/path

Generalize the parsing to work with each of these for all push URLs matching
*@*. Tested with the following URLs:

  ssh://git@git.pokylinux.org/poky-contrib
  ssh://git@git.pokylinux.org/poky-contrib.git
  git@git.pokylinux.org:poky-contrib
  git@git.pokylinux.org:poky-contrib.git

Signed-off-by: Darren Hart <dvhart@linux.intel.com>