mmc: core: Report firmware version for eMMC 5.0 devices.

For eMMC 5.0 compliant device, firmware version is stored in ext_csd.
Report firmware as a 64bit hexa decimal. Vendor can use hexa or ascii
string to report firmware version.
Also add FFU related EXT_CSD register and note if the device is FFU capable.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>