ARC: HSDK-4xD: make init status resistant to U-boot reloading

Use register intstead of static variable to store HSDK init status as
we want to avoid the situation when we reload U-boot via MDB after
previous init is done but HW reset (board reset) isn't done. So
let's store the init status in unused register - CREG_CPU_0_ENTRY
so status will survive after U-boot is reloaded via MDB.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>