Change in coreboot[master]: timestamp: Add new helper functions

[Bora Guvendik (Code Review)]

Attention is currently required from: Bora Guvendik, Furquan Shaikh, Subrata Banik, Julius Werner, Angel Pons, Aaron Durbin.
Bora Guvendik has uploaded a new patch set (#7) to the change originally created by Subrata Banik. ( https://review.coreboot.org/c/coreboot/+/51445 )

Change subject: timestamp: Add new helper functions
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timestamp: Add new helper functions

1. timestamp_rewind_base
   This function will rewind base_time in timestamp table using the delta provided in base_freq_mhz.
     * 1. Calculate base_delta_tick in ts->tick_freq_mhz using base_delta * ts->tick_freq_mhz / base_freq_mhz.
     * 2. Update all entries in timestamp table by adding base_delta_tick
     * 3. Update ts->base_time as ts->base_time - base_delta_tick

2. timestamp_add_relative
     * This function will add a new entry to timestamp table using the time_from_base expressed in freq_mhz
     * 1. Calculate time_from_base in ts->tick_freq_mhz using time_from_base * ts->tick_freq_mhz / freq_mhz.
     * 2. Call timestamp_add_table_entry using ts_table, id, time_from_base_tick

TEST=Rewind the base timestamp, add relative timestamps and verify cbmem -t output

Change-Id: I6b7065ed26e231fc898ae44bcc15cba6fb42b308
Signed-off-by: Subrata Banik 
Signed-off-by: Bora Guvendik 
---
M src/include/timestamp.h
M src/lib/timestamp.c
2 files changed, 78 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/45/51445/7