powerpc/machdep: Drop include of dma-mapping.h

Drop the include of dma-mapping.h in machdep.h, replace it with forward
declarations of struct device and struct pci_dev, and include time64.h
and page.h which are required for time64_t and pgprot_t respectively.

Add direct includes of some other headers to some files that were
getting them via machdep.h.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241009051826.132805-2-mpe@ellerman.id.au