linux-phytec-ti

Btrfs: remove repeated eb->pages check in, disk-io.c/csum_dirty_buffer

In csum_dirty_buffer, we first get eb from page->private.
Then we check if the page is the first page of eb. Later
we check it again. Remove the repeated check here.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>