cfi: make flash_get_info() non static

If on your board is more than one flash, you must know
the size of every single flash, for example, for updating
the DTS before booting Linux. So make this function
flash_get_info() extern, and you can have all info
about your flashes.

Signed-off-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>