UBUNTU: SAUCE: (no-up) dma-mapping: Remove WARN_ON in dma_free_coherent

UBUNTU: SAUCE: (no-up) dma-mapping: Remove WARN_ON in dma_free_coherent

BugLink: http://bugs.launchpad.net/bugs/458201

Triggered by the following backtrace:

WARNING: at
/build/buildd/linux-2.6.32/arch/x86/include/asm/dma-mapping.h:154
___free_dma_mem_cluster+0x102/0x110()

 [<ffffffff81064f9b>] warn_slowpath_common+0x7b/0xc0
 [<ffffffff81064ff4>] warn_slowpath_null+0x14/0x20
 [<ffffffff8139a2a2>] ___free_dma_mem_cluster+0x102/0x110
 [<ffffffff8139a072>] __sym_mfree+0xd2/0x100
 [<ffffffff8139a109>] __sym_mfree_dma+0x69/0x100
 [<ffffffff8139245f>] sym_hcb_free+0x8f/0x1f0

This patch never will be accepted upstream because the WARN_ON
is supposed to perevent driver development which is only
compatible with x86 on x86 (ARM can sleep in that function).
The right way to fix it would be to make the offending function
use locks in the right way but that requires careful implementation.

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>