GCC4.6: Squash warning in cmd_ubi.c:

cmd_ubi.c: In function ‘ubi_volume_read’:
cmd_ubi.c:319:9: warning: variable ‘count_save’ set but not used
[-Wunused-but-set-variable]

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>