btrfs: use booleans for delalloc arguments and struct find_free_extent_ctl

btrfs: use booleans for delalloc arguments and struct find_free_extent_ctl

The struct find_free_extent_ctl uses an int for the 'delalloc' field but
it's always used as a boolean, and its value is used to be passed to
several functions to signal if we are dealing with delalloc. The same goes
for the 'is_data' argument from btrfs_reserve_extent(). So change the type
from int to bool and move the field definition in the find_free_extent_ctl
structure so that it's close to other bool fields and reduces the size of
the structure from 144 down to 136 bytes (at the moment it's only declared
in the stack of btrfs_reserve_extent(), never allocated otherwise).

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>