The Vermilion Range Expansion Bus supports four chip selects, each of which
has 64MiB of address space.  The 2nd BAR of the Expansion Bus PCI Device
is a 256MiB memory region containing the address spaces for all four of
the chip selects, with start addresses hardcoded on 64MiB boundaries.

This map driver only supports NOR flash on chip select 0.  The buswidth
(either 8 bits or 16 bits) is determined by reading the Expansion Bus Timing
and Control Register for Chip Select 0 (EXP_TIMING_CS0).
Signed-off-by: Andy Lowe <alowe@mvista.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>