pata-rb532-cf: get rid of the irq_to_gpio() call

The RB532 platform specific irq_to_gpio() implementation has been
removed with commit 832f5dac ("MIPS: Remove all the uses of
custom gpio.h"). Now the platform uses the generic stub which causes
the following error:

  pata-rb532-cf pata-rb532-cf: no GPIO found for irq149
  pata-rb532-cf: probe of pata-rb532-cf failed with error -2

Drop the irq_to_gpio() call and get the GPIO number from platform
data instead. After this change, the driver works again:

  scsi host0: pata-rb532-cf
  ata1: PATA max PIO4 irq 149
  ata1.00: CFA: CF 1GB, 20080820, max MWDMA4
  ata1.00: 1989792 sectors, multi 0: LBA
  ata1.00: configured for PIO4
  scsi 0:0:0:0: Direct-Access     ATA      CF 1GB           0820 PQ: 0\
  ANSI: 5
  sd 0:0:0:0: [sda] 1989792 512-byte logical blocks: (1.01 GB/971 MiB)
  sd 0:0:0:0: [sda] Write Protect is off
  sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't\
  support DPO or FUA
   sda: sda1 sda2
  sd 0:0:0:0: [sda] Attached SCSI disk

Fixes: 832f5dac ("MIPS: Remove all the uses of custom gpio.h")
Cc: Alban Bedel <albeu@free.fr>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: <stable@vger.kernel.org> #v4.3+
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Tejun Heo <tj@kernel.org>