uboot-imx

Rewrote picos_to_clk() to avoid rounding errors.
Clarified that conversion is to DRAM clocks rather than platform clocks.
Made function static to spd_sdram.c.

Signed-off-by: James Yang <James.Yang@freescale.com>
Signed-off-by: Jon Loeliger <jdl@freescale.com>