Driver core: internal struct dma_coherent_mem, change type of a member.

struct dma_coherent_mem in drivers/base/dma-coherent.c
has member 'device_base' that is of type u32,
but is assigned value of type dma_addr_t, which may be
64 bits for x86_64. Change the type to dma_addr_t.

Signed-off-by: Marin Mitov <mitov@issp.bas.bg>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>