btrfs-progs: remove the unnecessary device_get_partition_size() call

Inside function _cmd_filesystem_usage_tabular(), there is a call of
device_get_partition_size() to calculate @unused.

However immediately after that call, @unused is updated using
devinfo->size, so that the previous call of device_get_partition_size()
is completely useless.

Just remove the unnecessary call.

And since we're here, also remove a dead newline in that loop at
variable declaration.

Fixes: 7ab0c46 ("btrfs-progs: fi usage: fix unallocated and print total and slack")
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>

Author: adam900710

cmds/filesystem-usage.c

@@ -959,7 +959,6 @@ static void _cmd_filesystem_usage_tabular(unsigned unit_mode,
 		int k;
 		const char *p;
 		const struct device_info *devinfo = devinfos->data[i];
-
 		u64  total_allocated = 0, unused;
 
 		p = strrchr(devinfo->path, '/');
@@ -1000,7 +999,6 @@ static void _cmd_filesystem_usage_tabular(unsigned unit_mode,
 			col++;
 		}
 
-		unused = device_get_partition_size(devinfo->path) - total_allocated;
 		unused = devinfo->size - total_allocated;
 
 		table_printf(matrix, unallocated_col, vhdr_skip + i, ">%s",