drm/amd/display: adding ddc_gpio_vga_reg_list to ddc reg def'ns

why:
oem-related ddc read/write fails without these regs

how:
copy from hw_factory_dcn20.c

Signed-off-by: Martin Leung <martin.leung@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>