subsys: random: xoroshiro128: Use entropy get isr during init

Current implementation of the xoroshiro depends on the ISR being
triggered when the interrupts is locked. This patch proposes
implementing the init with entropy_get_isr. This implementation
can be called at PRE_KERNEL_2 stage, even when the interrupts
are locked.

Fixes: GH-8199

Signed-off-by: Adithya Baglody <adithya.nagaraj.baglody@intel.com>