spi: spi-pxa2xx: Do not define 'struct acpi_device_id' when !CONFIG_ACPI

Since ACPI_PTR() is used to NULLify the value when !CONFIG_ACPI,
struct 'pxa2xx_spi_acpi_match' becomes defined but unused.

Fixes the following W=1 kernel build warning(s):

 drivers/spi/spi-pxa2xx.c:1435:36: warning: ‘pxa2xx_spi_acpi_match’ defined but not used [-Wunused-const-variable=]
 1435 | static const struct acpi_device_id pxa2xx_spi_acpi_match[] = {
 | ^~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Cc: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Link: https://lore.kernel.org/r/20200717135424.2442271-14-lee.jones@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>