drm/amd/display: Fix uninitialized field when expanding macro MI_DCE12_MASK_SH_LIST

Add back.

Fixes: 0cadcf7c

 ("drm/amd/display/dc/dce/dce_mem_input: Remove duplicate initialisation of GRPH_CONTROL__GRPH_NUM_BANKS_{SHIFT, MASK}")
Signed-off-by: Leslie Shi <Yuliang.Shi@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>