drm/radeon/kms: use linear aligned for evergreen/ni bo blits

Not only is linear aligned supposedly more performant,
linear general is only supported by the CB in single
slice mode.  The texture hardware doesn't support
linear general, but I think the hw automatically
upgrades it to linear aligned.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>