The __domain_mapping() always removes the pages in the range from
'iov_pfn' to 'end_pfn', but the 'end_pfn' is always the last pfn
of the range that the caller wants to map.

This would introduce too many duplicated removing and leads the
map operation take too long, for example:

  Map iova=0x100000,nr_pages=0x7d61800
    iov_pfn: 0x100000, end_pfn: 0x7e617ff
    iov_pfn: 0x140000, end_pfn: 0x7e617ff
    iov_pfn: 0x180000, end_pfn: 0x7e617ff
    iov_pfn: 0x1c0000, end_pfn: 0x7e617ff
    iov_pfn: 0x200000, end_pfn: 0x7e617ff
    ...
  it takes about 50ms in total.

We can reduce the cost by recalculate the 'end_pfn' and limit it
to the boundary of the end of this pte page.

  Map iova=0x100000,nr_pages=0x7d61800
    iov_pfn: 0x100000, end_pfn: 0x13ffff
    iov_pfn: 0x140000, end_pfn: 0x17ffff
    iov_pfn: 0x180000, end_pfn: 0x1bffff
    iov_pfn: 0x1c0000, end_pfn: 0x1fffff
    iov_pfn: 0x200000, end_pfn: 0x23ffff
    ...
  it only need 9ms now.

This also removes a meaningless BUG_ON() in __domain_mapping().
Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Tested-by: Liujunjie <liujunjie23@huawei.com>
Link: https://lore.kernel.org/r/20211008000433.1115-1-longpeng2@huawei.comSigned-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20211014053839.727419-10-baolu.lu@linux.intel.comSigned-off-by: Joerg Roedel <jroedel@suse.de>