MIPS: Print irq handler description

Add the name set by set_irq_chip_and_handler_name() to the output of
/proc/interrupts, like so:

db1200 ~ # cat /proc/interrupts
           CPU0
  8:         52     Alchemy-IC0-hilevel   serial
 10:        171     Alchemy-IC0-hilevel   au1xxx-mmc
 11:         47     Alchemy-IC0-hilevel   Au1xxx dbdma
 18:          1     Alchemy-IC0-hilevel   au1550-spi
 29:    1250997     Alchemy-IC0-riseedge  timer
 37:        211     Alchemy-IC0-hilevel   ehci_hcd:usb1, ohci_hcd:usb2
 38:          0     Alchemy-IC0-hilevel   lcd
 72:       2623     DB1200 CPLD-level     ide0
 73:        257     DB1200 CPLD-level     eth0
 84:          1     DB1200 CPLD-level     sd_insert
 85:          0     DB1200 CPLD-level     sd_eject

ERR:          0

Signed-off-by: Manuel Lauss <mano@roarinelk.homelinux.net>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>