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/page_64.h b/arch/powerpc/include/asm/page_64.h
index 932f88d..812b2cd 100644
--- a/arch/powerpc/include/asm/page_64.h
+++ b/arch/powerpc/include/asm/page_64.h
@@ -169,7 +169,7 @@
 /*
  * This is the default if a program doesn't have a PT_GNU_STACK
  * program header entry. The PPC64 ELF ABI has a non executable stack
- * stack by default, so in the absense of a PT_GNU_STACK program header
+ * stack by default, so in the absence of a PT_GNU_STACK program header
  * we turn execute permission off.
  */
 #define VM_STACK_DEFAULT_FLAGS32	(VM_READ | VM_WRITE | VM_EXEC | \