Looking at code the unsupported message comes from this supported udimms:
static const struct board_specific_parameters udimm0[] = {
/*
* memory controller 0
* num| hi| rank| clk| wrlvl | wrlvl | wrlvl
* ranks| mhz| GB |adjst| start | ctl2 | ctl3
*/
{1, 1666, 0, 0x8, 0x0D, 0x0C0B0A08, 0x0A0B0C08,}, // Got from rdimm0
{1, 1900, 0, 0x8, 0x0E, 0x0D0C0B09, 0x0B0C0D09,},
{1, 2300, 0, 0xa, 0x12, 0x100F0D0C, 0x0E0F100C,},
{2, 1350, 0, 8, 6, 0x0708090B, 0x0C0D0E09,},
{2, 1666, 0, 8, 7, 0x08090A0C, 0x0D0F100B,},
{2, 1900, 0, 8, 7, 0x09090B0D, 0x0E10120B,},
{2, 2300, 0, 8, 9, 0x0A0B0C10, 0x1213140E,},
{}
};
in "board/freescale/ls1046ardb/ddr.h"