[XENOPROF] Some fixes for xenoprof passive domain support.

[XENOPROF] Some fixes for xenoprof passive domain support.

Currently, passive domain samples are being assigned to the wrong
kernel functions. This patch fixes this problem. In addition the patch changes the
encoding of domain switch ESCAPE codes (marks used to separate samples
in oprofile  buffers associated with different domains). Instead of
using 2 codes, one  for START and one for END of passive domain
samples, a single escape CODE value is used to indicate a domain switch (no
need for a STOP followed by a START). Finally there some other minor style
fixes.

Signed-off-by: Jose Renato Santos <jsantos@hpl.hp.com>