For each NAND_OP_WAITRDY_INSTR operation, the NANDFSR register is
polled only once every 100 us to check for the EMA_WAIT pin. This
isn't frequent enough and causes delays in NAND accesses.
Set the polling interval to 0s. It increases the page read speed
reported by flash_speed by ~40% (~30% on page writes).
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Signed-off-by: Bastien Curutchet <bastien.curutchet@xxxxxxxxxxx>