Does pci_alloc_consisent really need to zero memory?

["Adam J. Richter" <adam@yggdrasil.com>]

	Is it really necessary for pci_alloc_consistent() to
fill the memory that it returns with all zeroes?  I don't
see anything in Documentation/DMA-mapping.txt that specifies
it.  I have been on the lookout for drivers that rely on it
for the past couple of months, and I haven't seen any.  It's
only one line of code in arch/i386/kernel/pci-dma.c, but it
is potentially a lot of cycles, even if only zeroes the
space you requested (rather than the full pages that it
actually allocates).

	If nobody objects in the next half day or so (or asks
me to follow some other course of action), I'll submit a patch for
2.5 for all architectures.

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