spi: Updates for v5.3

For the most part this is a quiet release for SPI, though there's
several of the more widely used drivers that have had some fairly
substantial development done on them, mainly improving
performance and adding support for some more obscure use cases.

 - Support for configuring a minimum time for chip select to be
   deasserted between transfers from Martin Sperl.
 - A rework of the ACPI device instantiation code from Ard
   Biesheuvel.
 - Fairly substantial development on the AT91 USART, BCM2835 and
   Tegra114 drivers.
 - New driver for Socionext SynQuacer.
Merge remote-tracking branch 'spi/topic/pump-rt' into spi-next