Adjust the size limit for splitting large files

Modify the number of max blocks per transfer to reduce splitting of
large files during patch generation. This will reduce the size of
final incremental OTA updater package. In specific, the size limit
for each file to transfer is set to 1/8 cachesize instead of a fix
number.

Bug: 26472126

Change-Id: Iffb135e378c4c7a91640f2fc4c40e9e93d1fe4bb
(cherry picked from commit bb86e1d9)