ftrace: add initial support for function profiling

FTrace allows to collect profiling stats for kernel functions.
This patch adds the initial support which allows to specify a list of
kernel function we would like to profile.

If a list of functions to profile is specified, for each specified function
we check for that function to be actually one of the available instrumented
functions which can be monitored by FTrace.
If a function is not supported, we throw an expection so that the user
is aware about the analysis which is going to do.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>