ARM: dts: rmobile: Add sysinfo extras on R-Car Gen3

Add sysinfo node and phandle to the board ID EEPROM on all boards
where this functionality is described in DT, which is Salvator-X(S),
ULCB and Ebisu. The u-boot,dm-pre-reloc is necessary here, since the
sysinfo must be available early during boot. The V3M and V3H boards
currently do not describe this board ID EEPROM in upstream DT, but
that could be easily added later, once the DTs contain the necessary
nodes.

ULCB and Ebisu needs the full EEPROM node in the u-boot extras DT,
since the EEPROM node is still missing in the upstream DTs. Ebisu
also needs extra compatible string override for the i2c_dvfs.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>