spi: xtensa-xtfpga: Use devm_platform_ioremap_resource() in xtfpga_spi_probe()

Simplify this function implementation by using a known wrapper function.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Link: https://lore.kernel.org/r/178bb78e-714f-645f-d819-5732870c4272@web.de


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