sched: EAS: fix idle_get_state_idx()

Consider a CPU is busy

- When a CPU has more than 1 runnable tasks but CPU is still
in idle state and about to exit or exiting idle state.

- When the CPU exits idle but idle_set_state_idx() is not
yet called.

Change-Id: I4830caf2828947be614a187c26e01e9b2950f1c1
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>