btrfs-progs: Use bool parameter to determine if we're allocating data extent

btrfs-progs: Use bool parameter to determine if we're allocating data extent

btrfs_reserve_extent() uses int @data to determine if we're allocating
data extent, while reuse the parameter later to pass it as profile
(data/meta/sys).

It's a little confusing, this patch will follow kernel parameter to use
bool @is_data to replace it.
And in btrfs_reserve_extent(), use dedicated u64 @profile.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Su Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>