ramips: mt7621_nand: reduce log verbosity

Avoid flooding the log with the message below by increasing the log
level to debug:

  mt7621-nand 1e003000.nand: Using programmed access timing: 31c07388
Signed-off-by: NStijn Tintel <stijn@linux-ipv6.be>
(cherry-picked from commit 89c19592)

target/linux/ramips/files/drivers/mtd/nand/raw/mt7621_nand.c

@@ -759,7 +759,7 @@ static int mt7621_nfc_setup_interface(struct nand_chip *nand, int csline,
 
 	acccon = ACCTIMING(tpoecs, tprecs, tc2r, tw2r, twh, twst, trlt);
 
-	dev_info(nfc->dev, "Using programmed access timing: %08x\n", acccon);
+	dev_dbg(nfc->dev, "Using programmed access timing: %08x\n", acccon);
 
 	nfi_write32(nfc, NFI_ACCCON, acccon);