ARM: shmobile: rcar-gen2: Remove explicit SYSC config and init

If the R-Car system controller is described in DT, the rcar-sysc driver
configures SYSCIER and SYSCIMR based on the SoC-specific power area
definitions in r8a779*-sysc.  The platform code still passed this
information to the rcar-sysc driver, for compatibility with old R-Car H2
and M2-W DTBs predating commit 8574de86 ("ARM: dts: r8a7791: Add
SYSC PM Domains") in v4.7.  The time has come to drop backwards
compatibility, and delegate everything to the DT enabled rcar-sysc
driver.

After the removal of the legacy SMP fallbacks, which powered up the SCUs
explicitly, there is no longer a need to force an early initialization
of the rcar-sysc driver.  It will be initialized in time for secondary
CPU bringup by its early_initcall().

Hence all explicit SYSC configuration and initialization can be removed
from the R-Car Gen2 platform code.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>