accel/qaic: Add bootlog debugfs

During the boot process of AIC100, the bootloaders (PBL and SBL) log
messages to device RAM. During SBL, if the host opens the QAIC_LOGGING
channel, SBL will offload the contents of the log buffer to the host,
and stream any new messages that SBL logs.

This log of the boot process can be very useful for an initial triage of
any boot related issues. For example, if SBL rejects one of the runtime
firmware images for a validation failure, SBL will log a reason why.

Add the ability of the driver to open the logging channel, receive the
messages, and store them. Also define a debugfs entry called "bootlog"
by hooking into the DRM debugfs framework. When the bootlog debugfs
entry is read, the current contents of the log that the host is caching
is displayed to the user. The driver will retain the cache until it
detects that the device has rebooted.  At that point, the cache will be
freed, and the driver will wait for a new log. With this scheme, the
driver will only have a cache of the log from the current device boot.
Note that if the driver initializes a device and it is already in the
runtime state (QSM), no bootlog will be available through this mechanism
because the driver and SBL have not communicated.

Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Carl Vanderlip <quic_carlv@quicinc.com>
Reviewed-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@quicinc.com>
Reviewed-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240322175730.3855440-2-quic_jhugo@quicinc.com