scripts: genpinctrl: handle pins with analog switch

This patch adds support for handling pins with analog switch (found in
H7 series). This feature was removed in a previous patch because it was
generating duplicate nodes. However, it removed some valid combinations.
This patch adds them back but with proper suffix (_c) avoiding duplicate
entries.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>