Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 1dafc86..4af1e2b 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -415,7 +415,7 @@
  *	@desc:	the interrupt description structure for this irq
  *
  *	Interrupt occures on the falling and/or rising edge of a hardware
- *	signal. The occurence is latched into the irq controller hardware
+ *	signal. The occurrence is latched into the irq controller hardware
  *	and must be acked in order to be reenabled. After the ack another
  *	interrupt can happen on the same source even before the first one
  *	is handled by the associated event handler. If this happens it