video: tegra: nvmap: implement full L2 clean/flush

When allocation is bigger than L2 size it is more optimal to
flush or writeback whole L2 instead of doing maintenance
for each allocated page.

bug 983964

Signed-off-by: Kirill Artamonov <kartamonov@nvidia.com>
Change-Id: Ieaa70875b92920567ad7cd75eca6eac8197f46de
Reviewed-on: http://git-master/r/108511
Reviewed-by: Simone Willett <swillett@nvidia.com>
Tested-by: Simone Willett <swillett@nvidia.com>