SF: use a switch for events in configureLocked()

HotplugEvent is an enum, and its cases should be handled from within a
switch case in configureLocked().

Improve readability and reduce indentation via this refactor.

Flag: EXEMPT refactor
Bug: 393126541
Test: libsurfaceflinger_unittest
Change-Id: Icb1ec5b7691ec9162af052bbce5c36192ee6952b