ide/ppc/pmac.c section fixes

This patch fixes the following section mismatch:

<--  snip  -->

...
WARNING: vmlinux.o(.text+0x3b641c): Section mismatch in reference from the function .pmac_ide_setup_device() to the function .init.text:.pmac_ide_setup_dma()
...

<--  snip  -->

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>