sata_nv: remove redundant pointers sdev0 and sdev1

Pointers sdev0 and sdev1 are being assigned but are never used hence they
are redundant and can be removed.

Cleans up clang warnings:
warning: variable 'sdev0' set but not used [-Wunused-but-set-variable]
warning: variable 'sdev1' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Tejun Heo <tj@kernel.org>