Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/arch/m68k/platform/coldfire/sltimers.c b/arch/m68k/platform/coldfire/sltimers.c
index 0a1b937..6a85daf 100644
--- a/arch/m68k/platform/coldfire/sltimers.c
+++ b/arch/m68k/platform/coldfire/sltimers.c
@@ -106,7 +106,7 @@
 	cycles = mcfslt_cnt;
 	local_irq_restore(flags);
 
-	/* substract because slice timers count down */
+	/* subtract because slice timers count down */
 	return cycles - scnt;
 }