mtd: rawnand: Fix a couple of spelling mistakes in Kconfig

There are two spelling mistakes in the Kconfig text. Fix them.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210704094705.37175-1-colin.king@canonical.com

drivers/mtd/nand/raw/Kconfig

@@ -480,9 +480,9 @@ config MTD_NAND_RICOH
 	select MTD_SM_COMMON
 	help
 	  Enable support for Ricoh R5C852 xD card reader
-	  You also need to enable ether
+	  You also need to enable either
 	  NAND SSFDC (SmartMedia) read only translation layer' or new
-	  expermental, readwrite
+	  experimental, readwrite
 	  'SmartMedia/xD new translation layer'
 
 config MTD_NAND_DISKONCHIP