libroot: remove delete_driver_settings

It is not present in BeOS R5 and it just call unload_driver_settings.

Replace delete_driver_settings usages with unload_driver_settings.
Keep the symbol on x86 for binary compatibility.

Change-Id: I1382710e3a4cb5c65d1249ea0e5880891e6800e4
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3485
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

btrfs: partially implement filesystem initialization

Change-Id: I7fb3340dc39b3331d30e5113b5860d936efab253
Reviewed-on: https://review.haiku-os.org/c/1395
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>