sunxi: Rename bus-width related macros in H3 DRAM code

sunxi: Rename bus-width related macros in H3 DRAM code

The DesignWare DRAM controller used by H3 and newer SoCs use a bit to
identify whether the DRAM is half-width.

As H3 itself come with 32-bit DRAM, the two modes of the bit used to be
named "MCTL_CR_32BIT" and "MCTL_CR_16BIT", but for SoCs with 16-bit DRAM
they're really 8-bit and 16-bit.

Rename the bit's macro, and also rename the variable name in
dram_sun8i_h3.c.

This commit do not add 16-bit DRAM controller support, but the support
will be introduced in next commit.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>