rockchip: pinctrl: rk3399: add support for the SPI5 controller

rockchip: pinctrl: rk3399: add support for the SPI5 controller

This commit adds support for the pin-configuration of the SPI5
controller of the RK3399 through the following changes:
 * grf_rk3399.h: adds definition for configuring the SPI5 pins
   		 in the GPIO2C group
 * periph.h: defines PERIPH_ID_SPI3 through PERIPH_ID_SPI5
 * pinctrl_rk3399.c: adds the reverse-mapping from the IRQ# to
   		     PERIPH_ID_SPI5; dispatches PERIPH_ID_SPI3
		     through SPI5 to the appropriate pin-config
		     function; implements the pin-configuration
		     for PERIPH_ID_SPI5 using the GPIO2C group

X-AffectedPlatforms: RK3399-Q7
Signed-off-by: Philipp Tomsich <[email protected]>
Tested-by: Jakob Unterwurzacher <[email protected]>
Acked-by: Simon Glass <[email protected]>