cnss2: Expose idle restart/shutdown APIs

Interface change to expose idle restart/shutdown APIs for WLAN
driver. This patch is to provide API interface to ease compilation
issues among various branches of kernel and WLAN driver. The actual
implementation will be in a separate patch.

Change-Id: I7f4a0079c32875c362d36c9f794d55609f924198
Signed-off-by: Yue Ma <yuem@codeaurora.org>