Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/arch/cris/arch-v32/drivers/mach-fs/nandflash.c b/arch/cris/arch-v32/drivers/mach-fs/nandflash.c
index c5a0f54..d5b0cc9 100644
--- a/arch/cris/arch-v32/drivers/mach-fs/nandflash.c
+++ b/arch/cris/arch-v32/drivers/mach-fs/nandflash.c
@@ -156,7 +156,7 @@
 	/* Enable the following for a flash based bad block table */
 	/* this->options = NAND_USE_FLASH_BBT; */
 
-	/* Scan to find existance of the device */
+	/* Scan to find existence of the device */
 	if (nand_scan(crisv32_mtd, 1)) {
 		err = -ENXIO;
 		goto out_ior;