Core-R: Make GIC and TIM configurable

Cortex-R may have integrated GIC and private timer,
this patch allow to enable or disable GIC and private timer
driver in cmsis package.

Zephyr already have a GIC driver, and platform may prefer to use
another driver or component for timer.

Give the choice to the caller to enable disable CMSIS driver
implementation.

Signed-off-by: Julien Massot <julien.massot@iot.bzh>