sam3x: report correct number of IRQ priority bits
sam3x: report correct number of IRQ priority bits

The Sam3x HAL defines __NVIC_PRIO_BITS to 4.
Fixes an issue where interrupt priorities and masking
were not being done correctly.

Issue: ZEP-2243
Signed-off-by: Andrew Boie <aab045b28152628be6af0e556050d0381fd0a34d@intel.com>

ldts/zephyr,nashif/zephyr,galak/zephyr,fbsder/zephyr,zephyriot/zephyr,fractalclone/zephyr-riscv,fbsder/zephyr,ldts/zephyr,punitvara/zephyr,punitvara/zephyr,mbolivar/zephyr,galak/zephyr,holtmann/zephyr,GiulianoFranchetto/zephyr,sharronliu/zephyr,runchip/zephyr-cc3220,kraj/zephyr,finikorg/zephyr,Vudentz/zephyr,ldts/zephyr,fractalclone/zephyr-riscv,fbsder/zephyr,fractalclone/zephyr-riscv,fbsder/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,fractalclone/zephyr-riscv,rsalveti/zephyr,Vudentz/zephyr,holtmann/zephyr,Vudentz/zephyr,rsalveti/zephyr,sharronliu/zephyr,explora26/zephyr,rsalveti/zephyr,aceofall/zephyr-iotos,aceofall/zephyr-iotos,galak/zephyr,holtmann/zephyr,runchip/zephyr-cc3220,rsalveti/zephyr,aceofall/zephyr-iotos,sharronliu/zephyr,explora26/zephyr,kraj/zephyr,runchip/zephyr-cc3220,punitvara/zephyr,aceofall/zephyr-iotos,Vudentz/zephyr,holtmann/zephyr,zephyrproject-rtos/zephyr,fractalclone/zephyr-riscv,sharronliu/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,rsalveti/zephyr,kraj/zephyr,explora26/zephyr,nashif/zephyr,aceofall/zephyr-iotos,sharronliu/zephyr,zephyriot/zephyr,finikorg/zephyr,explora26/zephyr,kraj/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,mbolivar/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,runchip/zephyr-cc3220,zephyriot/zephyr,zephyriot/zephyr,Vudentz/zephyr,fbsder/zephyr,mbolivar/zephyr,finikorg/zephyr,runchip/zephyr-cc3220,explora26/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,holtmann/zephyr,mbolivar/zephyr,mbolivar/zephyr,punitvara/zephyr,nashif/zephyr,finikorg/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,kraj/zephyr