utils/trace: update getTasks to use existing dataframes
utils/trace: update getTasks to use existing dataframes

We currently build a single _tasks_by_pid DF which allows to index tasks
both by PIDs and Name. The getTasksThis function, which usages have been
already removed from existing code, was intended to report a dictionary
mapping PIDs to task namess.

This patch update its definition to use the already existing _tasks_by_pid
dataframe, which has just to be returned as a dictionary.

Signed-off-by: Patrick Bellasi <431c86f368affbc3148c4669fbd465131f7e82cb@arm.com>

mdigiorgio/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,credp/lisa,arnoldlu/lisa,credp/lisa,arnoldlu/lisa,ARM-software/lisa,ARM-software/lisa,bjackman/lisa,bjackman/lisa,mdigiorgio/lisa