doc: add timer library changes to release notes
doc: add timer library changes to release notes

Signed-off-by: Erik Gabriel Carrillo <e875827104151a044027635d030c91d145f99619@intel.com>
Acked-by: John McNamara <af31595c36a4239b9676e9b3a777d3e2f15a6c4d@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk