habanalabs: support receiving ascii message from preboot f/w

An Ascii message that is sent from preboot towards the driver
will indicate the specific error that occurred on the f/w.
This commit supports that message and parse the ascii string
in order to print it into the kernel log

The commit also changes the way the descriptor struct is declared.
While its size increased (it now above 1024 bytes), it will be
allocated by using kmalloc instead of stack declaration.

Signed-off-by: Tal Cohen <talcohen@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>