xtensa: implement ccount calibration for s6000

Calculate core frequency from timers at boot time
instead of assuming a fixed frequency. This is
useful as the true frequency is set up by the
boot loader, thus variable.

Signed-off-by: Oskar Schirmer <os@emlix.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

diff --cc arch/xtensa/Kconfig
Simple merge

diff --cc arch/xtensa/variants/s6000/Makefile
Simple merge

diff --cc arch/xtensa/variants/s6000/delay.c
Simple merge