arm: at91sam9n12: change EBI IO to high drive mode

arm: at91sam9n12: change EBI IO to high drive mode

As both the DDR SDRAM and NAND flash connect to EBI on at91sam9n12
and share the lower 8 bits data line. If use low drive of the data
line, it will cause DDR data access corrupt in lower address, so
change the data line to high drive mode

This will fix the Linux kernel boot issue when use Lower address

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Andreas Bießmann <andreas.devel@googlemail.com>