Hi,

Here is the patch to fix few minor issues with pci_map_sg() and pci_map_cont()
for x86_64. I ran into these asserts while testing with qlogic fc driver.

The patch fixes following:

1) pci_map_sg() coalsces "sg" entries without modifying command's
"use_sg" value. It sets the "sg" entries length to "0" to indicate that
these entires are coalsced. If the command gets retried, the pci_map_sg() 
code trips on the assert that all entries length should be > 0.

2) __pci_map_cont() incorrectly assumes that "start" is always 0, so it
trips on few asserts.

Thanks,
Badari