chip/mt_scp/hrtimer: Change 26Mhz to a define
chip/mt_scp/hrtimer: Change 26Mhz to a define

Instead of hardcoding 25/26 all over the place, define the value
at the top of the file. That'll make it easier to change the
clock later.

BRANCH=none
BUG=b:134035444
TEST=make BOARD=kukui_scp -j && \
  bash board/kukui_scp/update_scp $IP

Change-Id: I32df164c172a624560c1299049269899211815ce
Signed-off-by: Nicolas Boichat <f3daba1cdc403799935674d3cd4b0e5bd1804232@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1672644
Reviewed-by: Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec