repair: remove unused strided secondary sb scan logic

repair: remove unused strided secondary sb scan logic

verify_set_primary_sb() scans and verifies secondary superblocks based
on the primary sb. It currently defines a maximum number of 8
superblocks to scan per iteration. It also implements a strided
algorithm that appears intended to ultimately scan every secondary,
albeit in a strided order.

Given that the algorithm is written to hit every sb and the stride value
is initialized as follows:

	num_sbs = MIN(NUM_SBS, rsb->sb_agcount);
	skip = howmany(num_sbs, rsb->sb_agcount);

... which is guaranteed to be 1 since the howmany() parameters are
backwards, the strided algorithm doesn't appear to accomplish anything
that can't be done with a simple for loop. In other words, despite the
max value and strided algorithm, repair always scans all of the
secondary superblocks in incremental order.

Therefore, remove the strided algorithm bits and replace with a simple
for loop. As a result of this cleanup, also remove the 'checked' buffer
used to track repeated ag visits and the now unused NUM_SBS definition.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>