arc: fix unaligned variables resulting in unaligned k_cpu_sleep_mode

Force-align all variables defined via asm .word to ensure 4-byte
alignment.

The straddled_tick_on_idle_enter variable was a bool, which resolved in
an one-byte quantity. Changing it to a 32-bit integer. It would have
occupied 4 bytes anyway with alignment.

Fixes ZEP-1549.

Change-Id: If5e0aa1a75dbc73d896b44616f059d221fe191c6
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
4 files changed