more davinci_emac sparse fixes

Update more of the RX and TX buffer descriptor (BD) handling to
properly distinguish between __iomem pointers and normal data
memory address space, getting rid of 32 "cast removes address
space of expression" messages.

This patch doesn't resolve all the issues sparse reports.  In fact
there are now 48 new "dereference of noderef expression" messages.
They mean that a patch is needed to convert BD member accessors to
use readl/writel calls.

Plus, there are several related issues that sparse won't warn about.
The initial i/o space addresses -- SRAM used for BDs, and controller
registers -- should come from ioremap.  Reverse mappings shouldn't
usually be needed, and if they are they should avoid io_v2p() and
virt_to_phys() calls.  And the need to use casts so often is wrong,
especially with __force annotations.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>