xtensa: timex.h: remove unused symbols

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Chris Zankel <chris@zankel.net>
xtensa: cleanup ccount frequency tracking

Remove unused nsec_per_ccount, and rename ccount_per_jiffy to ccount_preq.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Chris Zankel <chris@zankel.net>
xtensa: consolidate ccount access routines

Use get_ccount everywhere; remove xtensa_get_ccount.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Chris Zankel <chris@zankel.net>
xtensa: ccount based clockevent implementation

Reused some code from a preliminary implementation by Max Fillippov.

Cc: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Chris Zankel <chris@zankel.net>
xtensa: ccount based sched_clock

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Chris Zankel <chris@zankel.net>