arm: mvebu: clearfog: Fix SPI-NOR flash access

arm: mvebu: clearfog: Fix SPI-NOR flash access

The production variant of the SPI flash used by the clearfog
devices are based on winbond chips.  Additionally enable
SPI_FLASH_BAR since some variants will have 16MB of flash
that requires this to be enabled.

Remove the default speed and mode; these values are taken from the
device tree when CONFIG_DM_SPI_FLASH is enabled.

Add default bus, so that 'sf' detects the SPI flash by default.

Signed-off-by: Jon Nettleton <jon@solid-run.com>
[baruch: remove speed/mode; add bus; move winbond to defconfig]
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Stefan Roese <sr@denx.de>