MIPS: msi-octeon: eliminate kernel-doc warnings

Rearrange kernel-doc notation for 2 functions to eliminate
kernel-doc warnings. Use Return: notation for the function
return value description. Add function short descriptions
for both functions.
Correct 2 typos.

Fixes these kernel-doc warnings:

msi-octeon.c:49: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* Called when a driver request MSI interrupts instead of the
msi-octeon.c:49: warning: missing initial short description on line:
* Called when a driver request MSI interrupts instead of the
msi-octeon.c:62: warning: No description found for return value of 'arch_setup_msi_irq'
msi-octeon.c:189: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* Called when a device no longer needs its MSI interrupts. All
msi-octeon.c:189: warning: missing initial short description on line:
* Called when a device no longer needs its MSI interrupts. All

Fixes: e8635b484f64 ("MIPS: Add Cavium OCTEON PCI support.")
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Randy Dunlap <[e-mail]>
Cc: Aditya Srivastava <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: [e-mail]
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/pci/msi-octeon.c

···
 static int msi_irq_size;
 
 /**
- * Called when a driver request MSI interrupts instead of the
+ * arch_setup_msi_irq() - setup MSI IRQs for a device
+ * @dev:    Device requesting MSI interrupts
+ * @desc:   MSI descriptor
+ *
+ * Called when a driver requests MSI interrupts instead of the
  * legacy INT A-D. This routine will allocate multiple interrupts
  * for MSI devices that support them. A device can override this by
  * programming the MSI control bits [6:4] before calling
  * pci_enable_msi().
  *
- * @dev:    Device requesting MSI interrupts
- * @desc:   MSI descriptor
- *
- * Returns 0 on success.
+ * Return: %0 on success, non-%0 on error.
  */
 int arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc)
 {
···
 }
 
 /**
+ * arch_teardown_msi_irq() - release MSI IRQs for a device
+ * @irq:    The devices first irq number. There may be multiple in sequence.
+ *
  * Called when a device no longer needs its MSI interrupts. All
  * MSI interrupts for the device are freed.
- *
- * @irq:    The devices first irq number. There may be multple in sequence.
  */
 void arch_teardown_msi_irq(unsigned int irq)
 {