This patch renames the section 'Using Buildroot' into 'Buildroot quick
start' as real details about Buildroot usage will be in the User Guide
rather than in 'Getting Started'.
Additionally, add a cross-reference to the section about configuring
Buildroot.
Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>