SPI Engine: fix off-by-one sleep time (#1429)

Revert to behavior seen on first SPI Engine commit, expected by sw:
sleep t+1 ticks

Signed-off-by: Laez Barbosa <laez.barbosa@analog.com>

Author: LBFFilho

docs/library/spi_engine/instruction-format.rst

@@ -171,7 +171,7 @@ is the minimum, needed by the internal logic.
 
 .. math::
 
-   sleep\_time = \frac{2+(t) * ((div + 1) * 2)}{f_{clk}}
+   sleep\_time = \frac{2+(t+1) * ((div + 1) * 2)}{f_{clk}}
 
 .. list-table::
    :widths: 10 15 75
@@ -182,7 +182,7 @@ is the minimum, needed by the internal logic.
      - Description
    * - t
      - Time
-     - The amount of time to wait.
+     - The amount of prescaler cycles to wait, minus one.
 
 .. _spi_engine cs-invert-mask-instruction:
 

library/spi_engine/spi_engine_execution/spi_engine_execution.v

@@ -251,7 +251,7 @@ module spi_engine_execution #(
   assign trigger_tx = trigger == 1'b1 && ntx_rx == 1'b0;
   assign trigger_rx = trigger == 1'b1 && ntx_rx == 1'b1;
 
-  assign sleep_counter_compare = sleep_counter == cmd_d1[7:0];
+  assign sleep_counter_compare = sleep_counter == cmd_d1[7:0]+1;
   assign cs_sleep_counter_compare = cs_sleep_counter == cmd_d1[9:8];
   assign cs_sleep_early_exit = (cmd_d1[9:8] == 2'b00);