spi: axi-spi-engine: remove p from struct spi_engine_message_state

spi: axi-spi-engine: remove p from struct spi_engine_message_state

The program pointer p in struct spi_engine_message_state in the AXI SPI
Engine controller driver was assigned but never read so it can be
removed.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://msgid.link/r/20240304-mainline-axi-spi-engine-small-cleanups-v2-1-5b14ed729a31@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>