[BOLT] Fix jump table analysis for non-simple functions

Summary:
When we disassemble functions, we add discovered jump tables to a global
container in BinaryContext. Later, we analyze and verify all jump
tables. However, analysis for non-simple functions might fail for numerous
reasons, e.g. there would be no instruction at a destination. Since we
are not overwriting non-simple functions, it is not a critical error.
Thus, we can safely skip jump table analysis for non-simple functions.

(cherry picked from FBD18422997)