upstream_uboot.md: fix spi flash write command
Reported-by: Christopher Obbard chris.obbard@collabora.com Signed-off-by: Eugen Hristev eugen.hristev@collabora.com
Reported-by: Christopher Obbard chris.obbard@collabora.com Signed-off-by: Eugen Hristev eugen.hristev@collabora.com