drm/amd/display: Fix two cursor duplication when using overlay

Our driver supports overlay planes, and as expected, some userspace
compositor takes advantage of these features. If the userspace is not
enabling the cursor, they can use multiple planes as they please.
Nevertheless, we start to have constraints when userspace tries to
enable hardware cursor with various planes. Basically, we cannot draw
the cursor at the same size and position on two separated pipes since it
uses extra bandwidth and DML only run with one cursor.

For those reasons, when we enable hardware cursor and multiple planes,
our driver should accept variations like the ones described below:

  +-------------+   +--------------+
  | +---------+ |   |              |
  | |Primary  | |   | Primary      |
  | |         | |   | Overlay      |
  | +---------+ |   |              |
  |Overlay      |   |              |
  +-------------+   +--------------+

In this scenario, we can have the desktop UI in the overlay and some
other framebuffer attached to the primary plane (e.g., video). However,
userspace needs to obey some rules and avoid scenarios like the ones
described below (when enabling hw cursor):

                                      +--------+
                                      |Overlay |
 +-------------+    +-----+-------+ +-|        |--+
 | +--------+  | +--------+       | | +--------+  |
 | |Overlay |  | |Overlay |       | |             |
 | |        |  | |        |       | |             |
 | +--------+  | +--------+       | |             |
 | Primary     |    | Primary     | | Primary     |
 +-------------+    +-------------+ +-------------+

 +-------------+   +-------------+
 |     +--------+  |  Primary    |
 |     |Overlay |  |             |
 |     |        |  |             |
 |     +--------+  | +--------+  |
 | Primary     |   | |Overlay |  |
 +-------------+   +-|        |--+
                     +--------+

If the userspace violates some of the above scenarios, our driver needs
to reject the commit; otherwise, we can have unexpected behavior. Since
we don't have a proper driver validation for the above case, we can see
some problems like a duplicate cursor in applications that use multiple
planes. This commit fixes the cursor issue and others by adding adequate
verification for multiple planes.

Change since V1 (Harry and Sean):
- Remove cursor verification from the equation.

Cc: Louis Li <Ching-shih.Li@amd.com>
Cc: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Cc: Harry Wentland <Harry.Wentland@amd.com>
Cc: Hersen Wu <hersenxs.wu@amd.com>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>