Perf: Make per-process counters cumulative

In order to get overall value for performance counters, remove reset during
context switches. Add mechanism to calculate deltas for output to the trace
buffer.

Change-Id: I03d894a1b3bd400d8c256c3068f917ed001fbfd9
Signed-off-by: Sheetal Sahasrabudhe <sheetals@codeaurora.org>
Signed-off-by: Mekala Natarajan <mekalan@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Perf: Fix PID for tracepoints

Make previous value of PID a per_cpu variable.
This is required to get the correct value for previous_pid.

Change-Id: I63baf8164ae9226189c745339b122d806901789d
Signed-off-by: Sheetal Sahasrabudhe <sheetals@codeaurora.org>
Signed-off-by: Mekala Natarajan <mekalan@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>