drm/amd/display: dc/bios: add support for DCE6

[Why]
command_table_helper.c requires changes for DCE6 support

[How]
DCE6 targets added replicating and adapting the existing DCE8 implementation.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: fix incompatible structure layouts

Building the amd display driver with link-time optimizations revealed a bug
that caused dal_cmd_tbl_helper_dce80_get_table() and
dal_cmd_tbl_helper_dce110_get_table() get called with an incompatible
return type between the two callers in command_table_helper.c and
command_table_helper2.c:

drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce80/command_table_helper_dce80.h:31: error: type of 'dal_cmd_tbl_helper_dce80_get_table' does not match original declaration [-Werror=lto-type-mismatch]
const struct command_table_helper *dal_cmd_tbl_helper_dce80_get_table(void);

drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce80/command_table_helper_dce80.c:351: note: 'dal_cmd_tbl_helper_dce80_get_table' was previously declared here
const struct command_table_helper *dal_cmd_tbl_helper_dce80_get_table(void)

drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce110/command_table_helper_dce110.h:32: error: type of 'dal_cmd_tbl_helper_dce110_get_table' does not match original declaration [-Werror=lto-type-mismatch]
const struct command_table_helper *dal_cmd_tbl_helper_dce110_get_table(void);

drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce110/command_table_helper_dce110.c:361: note: 'dal_cmd_tbl_helper_dce110_get_table' was previously declared here
const struct command_table_helper *dal_cmd_tbl_helper_dce110_get_table(void)

The two versions of the structure are obviously derived from the same
one, but have diverged over time, before they got added to the kernel.

This moves the structure to a new shared header file and uses the superset
of the members, to ensure the interfaces are all compatible.

Fixes: ae79c310b1a6 ("drm/amd/display: Add DCE12 bios parser support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/dc: Add dc display driver (v2)

Supported DCE versions: 8.0, 10.0, 11.0, 11.2

v2: rebase against 4.11

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>