spi: cadence-xspi: Revert COMPILE_TEST support

spi: cadence-xspi: Revert COMPILE_TEST support

Commit 0c5b5c40dc31 ("spi: cadence-xspi: Add COMPILE_TEST support")
allows this driver to be built for 32-bit platforms, which causes a
semantic conflict with commit 4954d4eca469 ("spi: cadence-xspi: Support
32bit and 64bit slave dma interface"), as readsq() and writesq() are
only available when targeting 64-bit platforms:

  drivers/spi/spi-cadence-xspi.c: In function 'cdns_xspi_sdma_read':
  drivers/spi/spi-cadence-xspi.c:601:25: error: implicit declaration of function 'readsq'; did you mean 'readsl'? [-Wimplicit-function-declaration]
    601 |                         readsq(src, buf, len >> 3);
        |                         ^~~~~~
        |                         readsl
  drivers/spi/spi-cadence-xspi.c: In function 'cdns_xspi_sdma_write':
  drivers/spi/spi-cadence-xspi.c:623:25: error: implicit declaration of function 'writesq'; did you mean 'writesl'? [-Wimplicit-function-declaration]
    623 |                         writesq(dst, buf, len >> 3);
        |                         ^~~~~~~
        |                         writesl

As there are no known 32-bit platforms that use this controller, revert
compile testing support to restrict the driver to 64-bit platforms to
avoid burdening the driver with workarounds.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Fixes: 4954d4eca469 ("spi: cadence-xspi: Support 32bit and 64bit slave dma interface")
Acked-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://patch.msgid.link/20260606-spi-cadence-xspi-revert-compile-testing-v1-1-76219ea378bd@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>