dma-debug: update DMA debug API to better handle multiple mappings of a buffer

There were reports of the igb driver unmapping buffers without calling
dma_mapping_error.  On closer inspection issues were found in the DMA
debug API and how it handled multiple mappings of the same buffer.

The issue I found is the fact that the debug_dma_mapping_error would
only set the map_err_type to MAP_ERR_CHECKED in the case that the was
only one match for device and device address.  However in the case of
non-IOMMU, multiple addresses existed and as a result it was not setting
this field once a second mapping was instantiated.  I have resolved this
by changing the search so that it instead will now set MAP_ERR_CHECKED
on the first buffer that matches the device and DMA address that is
currently in the state MAP_ERR_NOT_CHECKED.

A secondary side effect of this patch is that in the case of multiple
buffers using the same address only the last mapping will have a valid
map_err_type.  The previous mappings will all end up...