arm: mvebu: Convert CRS305-1G-4S board to CRS3xx-98DX3236

Convert the CRS305-1G-4S board to CRS3xx-98DX3236 to enable easier
implementation of new CRS3xx series boards, based on Marvell Prestera
98DX3236.

Signed-off-by: Luka Kovacic <luka.kovacic@sartura.hr>
Reviewed-by: Stefan Roese <sr@denx.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Cc: Jakov Petrina <jakov.petrina@sartura.hr>