[coreboot-gerrit] Change in coreboot[master]: timestamp: Add helper fucntions

[Furquan Shaikh (Code Review)]

Attention is currently required from: Julius Werner, Angel Pons, Subrata Banik, Aaron Durbin.
Furquan Shaikh has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/51445 )

Change subject: timestamp: Add helper fucntions
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Patch Set 3:

(1 comment)

File src/include/timestamp.h:

https://review.coreboot.org/c/coreboot/+/51445/comment/15bdd1fd_af8bd35f 
PS3, Line 26:  * Add a new raw timestamp in microseconds into timestamp_table at index 'n'.
> This might be going a bit far, but what do we actually gain by keeping the timestamp table in TSC fr […]

IIUC, the reason why x86 platforms store in TSC frequency is because the timestamp values are basically the raw values read by using `rdtsc` instruction. Thus, in the normal case, there is no need for conversion. If the values are to be stored in usecs, then for each timestamp_get() call, rdtsc value will have to be converted using TSC frequency.