icnss2: Enhance debugging information

Print subsystem notify event string for wpss & modem instead of
event code. Print proper file type in log while downloading BDF
and REGDB file. Log the error immediately if request_firmware
API get fail.

Change-Id: I32a07895faf2bce640e0bfe89e348c36b02c5150
Signed-off-by: Vijay Patil <vijaylil@codeaurora.org>