mtd: rawnand: davinci: Reduce polling interval in NAND_OP_WAITRDY_INSTR

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 5 us. It increases the page read speed
reported by flash_speed by ~30% (~10% on page writes).

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: bastien-curutchet

drivers/mtd/nand/raw/davinci_nand.c

@@ -736,7 +736,7 @@ static int davinci_nand_exec_instr(struct davinci_nand_info *info,
 	case NAND_OP_WAITRDY_INSTR:
 		timeout_us = instr->ctx.waitrdy.timeout_ms * 1000;
 		ret = readl_relaxed_poll_timeout(info->base + NANDFSR_OFFSET,
-						 status, status & BIT(0), 100,
+						 status, status & BIT(0), 5,
 						 timeout_us);
 		if (ret)
 			return ret;