net: renesas: rswitch: do not write to MPSM register at init time

MPSM register is used to execute mdio bus transactions.
There is no need to initialize it early.

Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://patch.msgid.link/20241216071957.2587354-2-nikita.yoush@cogentembedded.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>