RDMA/usnic: Fix misuse of sysfs_emit_at

RDMA/usnic: Fix misuse of sysfs_emit_at

In commit e28bf1f03b01 ("RDMA: Convert various random sprintf sysfs _show
uses to sysfs_emit") I mistakenly used len = sysfs_emit_at to overwrite
the last trailing space of potentially multiple entry output.

Instead use a more common style by removing the trailing space from the
output formats and adding a prefixing space to the contination formats and
converting the final terminating output newline from the defective
	len = sysfs_emit_at(buf, len, "\n");
to the now appropriate and typical
	len += sysfs_emit_at(buf, len, "\n");

Fixes: e28bf1f03b01 ("RDMA: Convert various random sprintf sysfs _show uses to sysfs_emit")
Link: https://lore.kernel.org/r/5eb794b9c9bca0494d94b2b209f1627fa4e7b555.camel@perches.com
Reported-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>