drivers: spi: nrfx: Move MISO lines pull configuration to DT

After switching to nrfx 2.0.0, the Kconfig choice options that allowed
enabling of pull-up or pull-down for MISO lines in SPIs and SPIMs are
not properly supported, they are simply ignored. This commit restores
the possibility of applying pull configuration for MISO lines.

In earlier nrfx versions, the MISO pull configuration could be only
set globally, in nrfx_config files, for all SPI and SPIM instances
together. Since nrfx 2.0.0, this configuration can be applied per
instance. This commit takes advantage of this possibility and instead
of using a common Kconfig option as a global setting for all instances,
allows applying individual instance settings via devicetree.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>