drivers: sam: entropy: implement get_entropy_isr
drivers: sam: entropy: implement get_entropy_isr

The commit contributes the implementation of
get_entropy_isr API function for the SAM entropy
driver. The implementation is similar to get_entropy,
with the difference that it does not invoke k_yield()
when called with the ENTROPY_BUSYWAIT options flag set.
When the function is invoked without the ENTROPY_BUSYWAIT
flag, it simply returns whatever data is available,
without busy waiting on the RNG herdware.

Signed-off-by: Ioannis Glaropoulos <5921cc8bab7e1d4329f52fd8f6268f9692e3de80@nordicsemi.no>

Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,nashif/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr