Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/mtd/nand/ams-delta.c b/drivers/mtd/nand/ams-delta.c
index a067d09..bc65bf7 100644
--- a/drivers/mtd/nand/ams-delta.c
+++ b/drivers/mtd/nand/ams-delta.c
@@ -228,7 +228,7 @@
 					  AMS_DELTA_LATCH2_NAND_NCE |
 					  AMS_DELTA_LATCH2_NAND_NWP);
 
-	/* Scan to find existance of the device */
+	/* Scan to find existence of the device */
 	if (nand_scan(ams_delta_mtd, 1)) {
 		err = -ENXIO;
 		goto out_mtd;