drivers: timer: Add support for cc23x0 systim

Add support for systim to cc23x0 SoC.

Signed-off-by: Lars Thalian Morstad <l-morstad@ti.com>
Signed-off-by: Vebjorn Myklebust <v.myklebust@ti.com>
Signed-off-by: Stoyan Bogdanov <sbogdanov@baylibre.com>
Signed-off-by: Julien Panis <jpanis@baylibre.com>