[U-Boot] is it mandatory for SPL to support DM

[Jagan Teki]

SPL has a foot-print constraint, so fully switching a particular
subsystem like SPI or SPI Flash to DM would increase the size of it.

Possible areas to look at are (assume SPL_DM supported)
1) platdata
2) implement board or platform specific spl device driver which
bypassed the actual framework ex: spl_spi_sunxi.c

Do we have any other solutions? or any arguments on above step 2?

Jagan.