Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/lib/decompress_unxz.c b/lib/decompress_unxz.c
index cecd23d..9f34eb5 100644
--- a/lib/decompress_unxz.c
+++ b/lib/decompress_unxz.c
@@ -83,7 +83,7 @@
  *    safety_margin = 128 + uncompressed_size * 8 / 32768 + 65536
  *                  = 128 + (uncompressed_size >> 12) + 65536
  *
- * For comparision, according to arch/x86/boot/compressed/misc.c, the
+ * For comparison, according to arch/x86/boot/compressed/misc.c, the
  * equivalent formula for Deflate is this:
  *
  *    safety_margin = 18 + (uncompressed_size >> 12) + 32768