io-mapping: Specify mapping size for io_mapping_map_wc()

io-mapping: Specify mapping size for io_mapping_map_wc()

The ioremap() hidden behind the io_mapping_map_wc() convenience helper
can be used for remapping multiple pages. Extend the helper so that
future callers can use it for larger ranges.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Yishai Hadas <yishaih@mellanox.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: David Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: Luis R. Rodriguez <mcgrof@kernel.org>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: netdev@vger.kernel.org
Cc: linux-rdma@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Luis R. Rodriguez <mcgrof@kernel.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-3-git-send-email-chris@chris-wilson.co.uk