drm/amd/display: Fix __nedf2 undefined for 32 bit compilation

When we tried to compile DCN32/321 for 32-bit architecture, we got this
error message:

ERROR: modpost: "__nedf2" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!

This commit fixes this issue by rewriting a small part of the
dcn32_build_wm_range_table.

Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Fixes: 265280b9 ("drm/amd/display: add CLKMGR changes for DCN32/321")
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>