DMA_MODE_{READ,WRITE} are declared in asm-powerpc/dma.h and their
declarations there match the definitions.  Old declarations in
ppc4xx_dma.h are not right anymore (wrong type, to start with).
Killed them, added include of asm/dma.h where needed.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>