cnss2: Make sure PCIe/MHI is up before collecting RAM dump

There may be race condition between firmware assert and runtime PM
suspend. Hence make sure PCIe/MHI is up before collecting RAM dump.

Change-Id: I9a76bf96c4a72045d31449ed9f760e498ae78789
Signed-off-by: Yue Ma <yuem@codeaurora.org>