malloc: remove !gd handling

malloc: remove !gd handling

Following the previous patch, malloc() is never called before gd is set,
so we can remove the special-case check for this condition.

This reverts commit 854d2b9753e4 "dlmalloc: ensure gd is set for early
alloc".

Cc: Rabin Vincent <[email protected]>
Signed-off-by: Stephen Warren <[email protected]>
Reviewed-by: Tom Rini <[email protected]>
Reviewed-by: Simon Glass <[email protected]>