mtd-utils: ubihealthd: this tool does not depend on UBIFS

mtd-utils: ubihealthd: this tool does not depend on UBIFS

The "need_getrandom" check and result is used only for the "ubihealthd".
This tool is very important to have it around at run-time, while the
corresponding "mkfs.ubifs" tool is still optional (think about offline
generated ubifs images).
Since compiling "mkfs.ubifs" adds more dependencies (various shared
libraries), buildsystems for embedded devices will add these shared
libraries to the root filesystem even if "mkfs.ubifs" isn't used or
installed.

Thus, handling both tools independently makes sense. The previous behavior
is kept, e.g. if UBIFS support is enabled, it enables "ubihealthd" as well.

Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>