change the return value of get_fs_type from int to long.

The field fs_type field of fd_parms is already long
Additionally the glibc man page says "Using unsigned int for such variables suffices on most systems." referring the minimum width of variables holding fs_type
There are already fs_types who sets the highest bit (CIFS, BTRFS HPFS...) which interfere with the error check in dump_one_reg_file_cond (fs_type < 0) through the cast into signed int and after this into long

Fixes error while dumping programs on a btrfs partition

Signed-off-by: Markus Knetschke <markus.knetschke@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>