cnss2: Enhance debugfs support for device boot

Add the debugfs support for full power on sequence to boot device,
full power off sequence to shutdown device, PCIe link up/down and
powering off device only. It can help to debug device boot issues
without WLAN host driver.

Change-Id: Ie1e65719eff0918cf64d1f0926ec36cad1c869e6
CRs-fixed: 2059087
Signed-off-by: Yue Ma <yuem@codeaurora.org>