mtd: cfi: Zap cfi_flash_base in DM case

Embed the flash base into struct flash_info instead of having ad-hoc
static array in the code. This does not only remove static variable,
but also allows CFI-like controllers, ie. HyperFlash ones, to use most
of the CFI flash code by populating the flash_info with matching base
address.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Signed-off-by: Stefan Roese <sr@denx.de>