accel/qaic: Add mhi_qaic_cntl

Some of the MHI channels for an AIC100 device need to be routed to
userspace so that userspace can communicate directly with QSM. The MHI
bus does not support this, and while the WWAN subsystem does (for the same
reasons), AIC100 is not a WWAN device. Also, MHI is not something that
other accelerators are expected to share, thus an accel subsystem function
that meets this usecase is unlikely.

Create a QAIC specific MHI userspace shim that exposes these channels.

Start with QAIC_SAHARA which is required to boot AIC100 and is consumed by
the kickstart application as documented in aic100.rst

Each AIC100 instance (currently, up to 16) in a system will create a
chardev for QAIC_SAHARA. This chardev will be found as
/dev/<mhi instance>_QAIC_SAHARA
For example - /dev/mhi0_QAIC_SAHARA

Signed-off-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@quicinc.com>
Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Carl Vanderlip <quic_carlv@quicinc.com>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Reviewed-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Acked-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1679932497-30277-7-git-send-email-quic_jhugo@quicinc.com