[PATCH] libata: convert assert(xxx)'s in low-level drivers to WARN_ON(!xxx)'s

This patch converts all assert(xxx)'s in low-level drivers to
WARN_ON(!xxx)'s.  After this patch, there is no in-kernel user of the
libata assert() macro.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>