efikamx: remove drive strength function and roll its functionality into the DCD

Efika MX boards configure their DDR pad settings twice, one in the DCD generated
from imximage_*.cfg and again in init_drive_strength called before relocation.

Rather than doing this, roll the changes it makes into the DCD so DDR is set up
before a single line of code in U-Boot is run.

The settings are identical with this DCD block which is shorter (by 7 entries)
than the old one, and after the output of init_drive_strength since a lot of the
functionality in the existing DCD and init_drive_strength function was just
setting the POR defaults. This goes to explain some now-missing entries.

Several hundred rounds of mtest have been run to test the settings before and
after to confirm DDR is stable and no ill-effects have been found.

Signed-off-by: Matt Sealey <matt@genesi-usa.com>
Acked-by: Stefano Babic <sbabic@denx.de>