MTD internal API presently uses 32-bit values to represent device
size. This patch updates them to 64-bits but leaves the external API
unchanged.

In general, changing from 32-bit to 64-bit values cause little
or no changes to the majority of the code with the following
exceptions:
  - printk message formats;
  - division and modulus of 64-bit values (mtd_div_by_wb,
    mtd_div_by_eb may be used in some of such cases).

Was tested on phyFLEX i.MX6.

Signed-off-by: Dmitry Lavnikevich <d.lavnikevich@sam-solutions.com>
Signed-off-by: Grigory Milev <g.milev@sam-solutions.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>