soc: renesas: Remove duplicate setup of soc_device_attribute.family

As of commit 3f84aa5e

 ("base: soc: populate machine name in
soc_device_register if empty") in v6.4, soc_device_register() fills in
soc_device_attribute.family when it is still empty.  Hence the identical
code in renesas_soc_init() doing the same can be removed.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/4c5e4d0d1819028466748ed684254fec41aae816.1701696627.git.geert+renesas@glider.be