drm/amd/display: set variables dml*_funcs storage-class-specifier to static

smatch reports
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.c:44:24: warning: symbol
  'dml20_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.c:51:24: warning: symbol
  'dml20v2_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.c:58:24: warning: symbol
  'dml21_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.c:65:24: warning: symbol
  'dml30_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.c:72:24: warning: symbol
  'dml31_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.c:79:24: warning: symbol
  'dml314_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.c:86:24: warning: symbol
  'dml32_funcs' was not declared. Should it be static?

These variables are only used in one file so should be static.
Cleanup whitespace, use tabs consistently for indents.

Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>