Update NetworkEquipment.php - Stacked switch Name with ID

[Mirkk]

Stacked switches got a name with the "description" (model) field added, all switches the same(!), which gives several issues in managing them, and has apparently no logic.

It seems that this was just a wrong copy-paste from the previous code line. Corrected with _$stack_number as a commonly used naming scheme.

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	no ticket