d2: Disable entropy gathering for MMC device

 * Flash devices aren't a good source of entropy and contributing to the
   pool can be an expensive operation requiring needless locking.

Change-Id: I6073b38476706c2e678ecf980ca0a1546cda9125
Merge pull request #1 from CyanogenMod/cm-10.1

d2: Disable entropy gathering for MMC device