cnss2: Add idle shutdown and restart support

If WLAN interface is not brought up for certain amount of time
after it is created, idle shutdown will happen to power off WLAN
device. Idle restart will happen to power up WLAN device if WLAN
is needed by user again. Add the support in platform driver.

Change-Id: Ie9486bbfda38fe22180f53875689a215d9882e67
Signed-off-by: Yue Ma <yuem@codeaurora.org>