Revert "vp9_ethread: include a pointer to mb in VP9_COMP"

This reverts commit 6906d218ddd1af97228a797f4558e402231d94f1.

Another way will be used to handle mb struct.

Change-Id: Ic1111a46b2b1ee00f8f9e3fcd4cf3eb6030b2dc4
14 files changed