global_data.h: drop write-only field dm_root_f

The dm_root_f field seems to be entirely write-only and hence
redundant, unless 'git grep' fails to find some access generated via
preprocessor token concatenation or similar.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Simon Glass <sjg@chromium.org>
3 files changed