ARM: shmobile: r8a7740: Prepare for reference DT setup

We need three steps to prepare for the new Armadillo reference DT board code:
 - Split the device list into r8a7740_early_devices used by the old platform
   data setup (board-armadillo.c) and r8a7740_devices_dt used by both
   setup variants.
 - Introduce new r8a7740_init_delay() to be more flexible about calling
   shmobile_setup_delay().
 - For the generic r8a7740 support, we switch to device tree setup for
   the GIC, the irqpin devices and the I2C controllers.

This is slightly similar to commit 3b00f934
"ARM: shmobile: sh73a0: Do not use early devices with DT reference"

Signed-off-by: Bastian Hecht <hechtb+renesas@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>