COIL: update chip/stm32/hwtimer.c
COIL: update chip/stm32/hwtimer.c

This CL updates chip/stm32/hwtimer.c according to the COIL guidelines.
This CL replaces "master" with "primary" and "slave" with "secondary".

BRANCH=None
BUG=b:163885307
TEST=compare_build.sh -b twinkie matches (CHIP_FAMILY_STM32F0)
     compare_build.sh -b discovery matches (!CHIP_FAMILY_STM32F0/F3)
     CHIP_FAMILY_STM32F3 could not be tested since no boards are
     triggering that part of the code. Tested with "make buildall"
     with invalid code in that part of the branch, and it compiled fine.

Change-Id: Ib3c941f5cf24edf9200a1acfca270e757e7e9ced
Signed-off-by: Ricardo Quesada <8b34ddfcea8f3287dba206edf399437d78820ea1@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3565045
Tested-by: Ricardo Quesada <8b34ddfcea8f3287dba206edf399437d78820ea1@chromium.org>
Reviewed-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>
Commit-Queue: Ricardo Quesada <8b34ddfcea8f3287dba206edf399437d78820ea1@chromium.org>
Auto-Submit: Ricardo Quesada <8b34ddfcea8f3287dba206edf399437d78820ea1@chromium.org>

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