#1833 breaks Tang nano 9k, as it generates illegal code

[andelf]

          @trabucayre @enjoy-digital  This breaks Tang nano 9k, as it generates illegal code:

ERROR (EX3637) : Range is not allowed in a prefix("/data/LiteX/litex-boards/litex_boards/targets/build/sipeed_tang_nano_9k/gateware/sipeed_tang_nano_9k.v":2633)
ERROR (EX3878) : 'IO_psram_dq' is not a memory("/data/LiteX/litex-boards/litex_boards/targets/build/sipeed_tang_nano_9k/gateware/sipeed_tang_nano_9k.v":2633

IOBUF IOBUF(
	// Inputs.
	.I   (main_hyperram_tstriple0_o[0]),
	.OEN ((~main_hyperram_tstriple0_oe)),

	// Outputs.
	.O   (main_hyperram_tstriple0_i[0]),

	// InOuts.
	.IO  (IO_psram_dq[7:0][0])
);

Originally posted by @andelf in #1833 (comment)

[trabucayre]

Indeed.
I have disabled Tristate support (after check with tangMega) and I have to find a valid fix.
thanks!