cnss2: Add debugfs support to simulate device and firmware boot

Add debugfs interface to simulate device and firmware boot step
by step. This can provide the flexibility to debug both host and
device issues in boot path. The debugfs node will only be added
in debug builds.

Change-Id: I4cf03efad5e5a792095f509864fddd54dc6e2e7c
CRs-fixed: 2059087
Signed-off-by: Yue Ma <yuem@codeaurora.org>