blance: Disable CONFIG_CMD_SF / CONFIG_CMD_SPI

The config header for this platform disables both CMD_SF and CMD_SPI and
the defconfig leaves them enabled.  Disable them from the defconfig and
enable them in the header.

Cc: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Masakazu Mochizuki <masakazu.mochizuki.wd@hitachi.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
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This is a case where it's hard to tell if this is the correct fix or if
both should be enabled instead.