arm: mvebu: Set common SPI flash default speed and mode

arm: mvebu: Set common SPI flash default speed and mode

CONFIG_SF_DEFAULT_SPEED is used in SPL SPI to configure and probe the
flash device during DM SPI uclass probing process, if the
spi-max-frequency is not available in the DTB. Currently the max
frequency is not available, because of the probing mechanism in SPI
uclass has not been fully updated to DM.

The CONFIG_SF_DEFAULT_SPEED is set to 1Mhz if a board defconfig
does not specify it. This speed is too slow and result in a few
seconds delay while the u-boot image is loaded from flash. Based on a
survey of the device tree specifications for MVEBU boards, a sane default
value should be 10Mhz. The default of 10Mhz enables an almost
instantaneously loading of the u-boot image.

Note that this patch depends on this patch series (has been merged to
u-boot-marvell/next):
https://lists.denx.de/pipermail/u-boot/2023-March/511038.html

- RESEND: correct spelling of SF_DEFAULT_MODE

Signed-off-by: Tony Dinh <mibodhi@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>