soc/integration/soc_sdram: simplify/fix main_ram_size computation using new databits value of the phy

litex/soc/integration/soc_sdram.py

@@ -62,13 +62,10 @@ class SoCSDRAM(SoCCore):
         self.submodules.sdram = ControllerInjector(
             phy, geom_settings, timing_settings, **kwargs)
 
-        dfi_databits_divisor = 1 if phy.settings.memtype == "SDR" else 2
-        sdram_width = phy.settings.dfi_databits//dfi_databits_divisor
+        # TODO: modify mem_map to allow larger memories.
         main_ram_size = 2**(geom_settings.bankbits +
                             geom_settings.rowbits +
-                            geom_settings.colbits)*sdram_width//8
-
-        # TODO: modify mem_map to allow larger memories.
+                            geom_settings.colbits)*phy.settings.databits//8
         main_ram_size = min(main_ram_size, 256*1024*1024)
         self.add_constant("L2_SIZE", self.l2_size)