raimps: mtk_eth_soc: drop rst_esw from ESW driver

raimps: mtk_eth_soc: drop rst_esw from ESW driver

The ESW core needs to be reset together with FE core, so after the
relevant reset controller lines are moved under FE, drop rst_esw and all
related code, which would not execute anyway, because rst_esw would be
NULL. While at that, ensure that if reset line for EPHY cannot be
claimed, a proper error message is reported.

Fixes: 60fadae62b64 ("ramips: ethernet: ralink: move reset of the esw into the esw instead of fe")
Co-developed-by: Maxim Anisimov <maxim.anisimov.ua@gmail.com>
Signed-off-by: Maxim Anisimov <maxim.anisimov.ua@gmail.com>
[Split out of the bigger commit, provide commit mesage, refactor error
handling]
Signed-off-by: Lech Perczak <lech.perczak@gmail.com>