drm/amd/display: Update swizzle mode enums

drm/amd/display: Update swizzle mode enums

BugLink: https://bugs.launchpad.net/bugs/1952579
commit 58065a1e524de30df9a2d8214661d5d7eed0a2d9 upstream.

[Why]
Swizzle mode enum for DC_SW_VAR_R_X was existing,
but not mapped correctly.

[How]
Update mapping and conversion for DC_SW_VAR_R_X.

Reviewed-by: XiangBing Foo <XiangBing.Foo@amd.com>
Reviewed-by: Martin Leung <Martin.Leung@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Cc: stable@vger.kernel.org
Tested-by: Daniel Wheeler <Daniel.Wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>