accel/amdxdna: Check interrupt register before mailbox_rx_worker exits

accel/amdxdna: Check interrupt register before mailbox_rx_worker exits

There is a timeout failure been found during stress tests. If the firmware
generates a mailbox response right after driver clears the mailbox channel
interrupt register, the hardware will not generate an interrupt for the
response. This causes the unexpected mailbox command timeout.

To handle this failure, driver checks the interrupt register before
exiting mailbox_rx_worker(). If there is a new response, driver goes back
to process it.

Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Reviewed-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250226161810.4188334-1-lizhi.hou@amd.com