some checkstyle fixes

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
switch to etnaviv_ and ETNA_ prefixes

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
rename files to reflect driver name

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
rename folder

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>