Fix build by adding `cbmem.c` to `COLLECT_TIMESTAMPS`

A board without HAVE_ACPI_RESUME did not build with
COLLECT_TIMESTAMPS enabled as `cbmem.c` was not built.

Change-Id: I9c8b575d445ac566a2ec533d73080bcccc3dfbca
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/2549
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc.jones@se-eng.com>
1 file changed