This renames dram.c and dram.h to dfs.c and dfs.h respectively. This
is to make room for common functionality between frequency scaling and
suspend code for the DRAM in a pair of common files named dram.c and
dram.h. It also removes a duplicate enum definition from
dram_spec_timing.h

Change-Id: Ibfa1041f8781401f9d27901fe8c61862bcb05562
Signed-off-by: Derek Basehore <dbasehore@chromium.org>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>