maple_tree: Fix skip entries on spanning adds and issue in split data

maple_tree: Fix skip entries on spanning adds and issue in split data

When spanning adds hit a skip entry, they were not updated and thus
future events may use the incorrect minimum from the previous
not-updated pivot.  Fix these pivots when writing spanning adds.

There was also an issue with using the incorrect ranges in the split
code path in mas_append_split_data() which could cause data to be
skipped.  This is now fixed and there are testcases to test for the
discovered event.

The spanning add issue was tested with set25 in check_erase2_testset.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>