ubi-utils: mtdinfo: Fix type truncation compiling warning for 'start' variable

ubi-utils: mtdinfo: Fix type truncation compiling warning for 'start' variable

Fix following compiling warning by using the right format:
 ubi-utils/mtdinfo.c:207:21: warning: format ‘%lx’ expects argument of
 type ‘long unsigned int’, but argument 4 has type ‘long long unsigned
 int’

Fixes: 78f4f38bd3de8 ("ubi-utils: Fix integer overflow in mtdinfo.c")
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>