btrfs: process inline extent earlier in replay_one_extent()

Instead of having an if statement to check for regular and prealloc
extents first, process them in a block, and then following with an else
statement to check for an inline extent, check for an inline extent first,
process it and jump to the 'update_inode' label, allowing us to avoid
having the code for processing regular and prealloc extents inside a
block, reducing the high indentation level by one and making the code
easier to read and avoid line splittings too.

Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>