support/scripts: prepare expanding the packages lists

Move to a function the code generating the package name from a
symbol's name, to avoid code duplication.

This is not used currently, but will be in a subsequent patch.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Samuel Martin <s.martin49@gmail.com>
Acked-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>