spi: efm32: Convert to use GPIO descriptors

This switches the EFM32 driver over to use the GPIO descriptor
handling in the core. The GPIO handling in this driver is
pretty simplistic so this should just work. Drop the GPIO headers
and insert the implicitly included <linux/of.h> header.

Signed-off-by: Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Uwe Kleine-König <u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Link: https://lore.kernel.org/r/20200317094914.331932-1-linus.walleij@linaro.org


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