target/rd: Refactor rd_build_device_space + rd_release_device_space
target/rd: Refactor rd_build_device_space + rd_release_device_space

This patch refactors rd_build_device_space() + rd_release_device_space()
into rd_allocate_sgl_table() + rd_release_device_space() so that they
may be used seperatly for setup + release of protection information
scatterlists.

Also add explicit memset of pages within rd_allocate_sgl_table() based
upon passed 'init_payload' value.

v2 changes:
  - Drop unused sg_table from rd_release_device_space (Wei)

Cc: Martin K. Petersen <0384aaef27f06874adbdb09a807bb339f4aff9fd@oracle.com>
Cc: Christoph Hellwig <923f7720577207a44b32e59bbfbea59d27f1ae8e@lst.de>
Cc: Hannes Reinecke <b0d1e9e4a4e27620745ff49be9000da3174a4cc6@suse.de>
Cc: Sagi Grimberg <380ce2a82d3d08e67ab163b51dc6d30288ad3f13@mellanox.com>
Cc: Or Gerlitz <de1b678a59344538ef9f2ddb34a5f9486544e2f9@mellanox.com>
Signed-off-by: Nicholas Bellinger <978acd1567d5598152161fdf8bf3ca568f950c9b@linux-iscsi.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs