ARM: dts: imx6ull: fix ubi filesystem mount failed

For NAND Ecc layout, there is a dependency from old kernel's nand driver
setting and current. if old kernel use 4 bit ecc , we should use 4 bit
in new kernel either. else will run into following error at filesystem
mounting.

So, enable fsl,use-minimum-ecc from device tree, to fix this mismatch

[    9.449265] ubi0: scanning is finished
[    9.463968] ubi0 warning: ubi_io_read: error -74 (ECC error) while reading
22528 bytes from PEB 513:4096, read only 22528 bytes, retry
[    9.486940] ubi0 warning: ubi_io_read: error -74 (ECC error) while reading
22528 bytes from PEB 513:4096, read only 22528 bytes, retry
[    9.509906] ubi0 warning: ubi_io_read: error -74 (ECC error) while reading
22528 bytes from PEB 513:4096, read only 22528 bytes, retry
[    9.532845] ubi0 error: ubi_io_read: error -74 (ECC error) while reading
22528 bytes from PEB 513:4096, read 22528 bytes

Fixes: f9ecf10c

 ("ARM: dts: imx6ull: add MYiR MYS-6ULX SBC")
Signed-off-by: dillon min <dillon.minfei@gmail.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>