Btrfs: remove no longer used function extent_read_full_page_nolock()

Not needed after the previous patch named
"Btrfs: fix page reading in extent_same ioctl leading to csum errors".

Signed-off-by: Filipe Manana <fdmanana@suse.com>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index c473c42..3346cd8 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -637,11 +637,7 @@
 	faili = nr_pages - 1;
 	cb->nr_pages = nr_pages;
 
-	/* In the parent-locked case, we only locked the range we are
-	 * interested in.  In all other cases, we can opportunistically
-	 * cache decompressed data that goes beyond the requested range. */
-	if (!(bio_flags & EXTENT_BIO_PARENT_LOCKED))
-		add_ra_bio_pages(inode, em_start + em_len, cb);
+	add_ra_bio_pages(inode, em_start + em_len, cb);
 
 	/* include any pages we added in add_ra-bio_pages */
 	uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;