Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/arch/powerpc/include/asm/uninorth.h b/arch/powerpc/include/asm/uninorth.h
index f737732..ae9c899 100644
--- a/arch/powerpc/include/asm/uninorth.h
+++ b/arch/powerpc/include/asm/uninorth.h
@@ -60,7 +60,7 @@
  *
  * Obviously, the GART is not cache coherent and so any change to it
  * must be flushed to memory (or maybe just make the GART space non
- * cachable). AGP memory itself doens't seem to be cache coherent neither.
+ * cachable). AGP memory itself does't seem to be cache coherent neither.
  *
  * In order to invalidate the GART (which is probably necessary to inval
  * the bridge internal TLBs), the following sequence has to be written,