Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/isdn/hardware/mISDN/hfcmulti.c b/drivers/isdn/hardware/mISDN/hfcmulti.c
index 4e3780d..f6f3c87 100644
--- a/drivers/isdn/hardware/mISDN/hfcmulti.c
+++ b/drivers/isdn/hardware/mISDN/hfcmulti.c
@@ -118,7 +118,7 @@
  *	-> See hfc_multi.h for HFC_IO_MODE_* values
  *	By default, the IO mode is pci memory IO (MEMIO).
  *	Some cards require specific IO mode, so it cannot be changed.
- *	It may be usefull to set IO mode to register io (REGIO) to solve
+ *	It may be useful to set IO mode to register io (REGIO) to solve
  *	PCI bridge problems.
  *	If unsure, don't give this parameter.
  *
@@ -903,7 +903,7 @@
 /*
  * Speech Design resync feature
  * NOTE: This is called sometimes outside interrupt handler.
- * We must lock irqsave, so no other interrupt (other card) will occurr!
+ * We must lock irqsave, so no other interrupt (other card) will occur!
  * Also multiple interrupts may nest, so must lock each access (lists, card)!
  */
 static inline void