firmware: stratix10-svc: Add Multi SVC clients support

In the current implementation, SVC client drivers such as socfpga-hwmon,
intel_fcs, stratix10-soc, stratix10-rsu each send an SMC command that
triggers a single thread in the stratix10-svc driver. Upon receiving a
callback, the initiating client driver sends a stratix10-svc-done signal,
terminating the thread without waiting for other pending SMC commands to
complete. This leads to a timeout issue in the firmware SVC mailbox service
when multiple client drivers send SMC commands concurrently.

To resolve this issue, a dedicated thread is now created per channel. The
stratix10-svc driver will support up to the number of channels defined by
SVC_NUM_CHANNEL. Thread synchronization is handled using a mutex to prevent
simultaneous issuance of SMC commands by multiple threads.

SVC_NUM_DATA_IN_FIFO is reduced from 32 to 8, since each channel now has
its own dedicated FIFO and the SDM processes commands one at a time.
8 entries per channel is sufficient while keeping the total aggregate
capacity the same (4 channels x 8 = 32 entries).

Additionally, a thread task is now validated before invoking kthread_stop
when the user aborts, ensuring safe termination.

Timeout values have also been adjusted to accommodate the increased load
from concurrent client driver activity.

Fixes: 7ca5ce8 ("firmware: add Intel Stratix10 service layer driver")
Cc: stable@vger.kernel.org
Signed-off-by: Ang Tien Sung <tien.sung.ang@altera.com>
Signed-off-by: Fong, Yan Kei <yankei.fong@altera.com>
Signed-off-by: Muhammad Amirul Asyraf Mohamad Jamian <muhammad.amirul.asyraf.mohamad.jamian@altera.com>
Link: https://lore.kernel.org/all/20260305093151.2678-1-muhammad.amirul.asyraf.mohamad.jamian@altera.com
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

Author: Muhammad Amirul Asyraf Mohamad Jamian