arch: arc: use the way of GEN_PRIV_STACK for privilege stack

drop the original C macro based allocation of privilged stack as
it may cause the waste of memory for ARC MPUv2.

now use the way of GEN_PRIV_STACK to generate privilege stack as
other archs did, e.g. ARM.

Signed-off-by: Wayne Ren <wei.ren@synopsys.com>
8 files changed