ide: build-fix for CONFIG_BLK_DEV_IDEDMA_PMAC=n

IDE pmac host driver build fails with CONFIG_BLK_DEV_IDEDMA_PMAC=n
as reported by Kamalesh:

> drivers/ide/pmac.c: In function 'pmac_ide_set_pio_mode':
> drivers/ide/pmac.c:527: error: implicit declaration of function 'kauai_lookup_timing'
> drivers/ide/pmac.c:527: error: 'shasta_pio_timings' undeclared (first use in this function)
> drivers/ide/pmac.c:527: error: (Each undeclared identifier is reported only once
> drivers/ide/pmac.c:527: error: for each function it appears in.)
> drivers/ide/pmac.c:534: error: 'kauai_pio_timings' undeclared (first use in this function)
> drivers/ide/pmac.c: In function 'pmac_ide_do_resume':
> drivers/ide/pmac.c:914: error: 'IDE_WAKEUP_DELAY' undeclared (first use in this function)
> drivers/ide/pmac.c: At top level:
> drivers/ide/pmac.c:1007: error: 'pmac_ide_init_dma' undeclared here (not in a function)
> drivers/ide/pmac.c: In function 'pmac_ide_setup_device':
> drivers/ide/pmac.c:1107: error: 'IDE_WAKEUP_DELAY' undeclared (first use in this function)
> drivers/ide/pmac.c: In function 'pmac_ide_macio_attach':
> drivers/ide/pmac.c:1209: error: 'pmac_ide_hwif_t' has no member named 'dma_regs'
> drivers/ide/pmac.c:1210: error: 'pmac_ide_hwif_t' has no member named 'dma_regs'
> make[2]: *** [drivers/ide/pmac.o] Error 1

Fix it by removing the superfluous config option.

Reported-and-tested-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>