amdgpu/dc: fix non-ansi function decls.

smatch reported:
drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce80/command_table_helper_dce80.c:351:71: warning: non-ANSI function declaration of function 'dal_cmd_tbl_helper_dce80_get_table'
drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce110/command_table_helper_dce110.c:361:72: warning: non-ANSI function declaration of function 'dal_cmd_tbl_helper_dce110_get_table'
drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce112/command_table_helper_dce112.c:415:72: warning: non-ANSI function declaration of function 'dal_cmd_tbl_helper_dce112_get_table'
drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce112/command_table_helper2_dce112.c:415:73: warning: non-ANSI function declaration of function 'dal_cmd_tbl_helper_dce112_get_table2'
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_surface.c:148:34: warning: non-ANSI function declaration of function 'dc_create_gamma'
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_surface.c:178:50: warning: non-ANSI function declaration of function 'dc_create_transfer_func'

This fixes them.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>