soc: renesas: Register SoC device early

The r8a7795 SYSC driver manages PM Domains, and thus is initialized from
an early_initcall().  However, this means the driver cannot check the
SoC revision, as the SoC device hasn't been registered yet.

Change renesas_soc_init() from a core_initcall() to an early_initcall()
to fix this (renesas-soc.o is listed before rcar-sysc.o in the Makefile).

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