Revert "i965: Don't add barrier deps for FB write messages."

Revert "i965: Don't add barrier deps for FB write messages."

This reverts commit d0e1d6b7e27bf5f05436e47080d326d7daa63af2.

The change in the vec4 code is a mistake -- there's never an
FS_OPCODE_FB_WRITE in vec4 code.

The change in the fs code had the (harmless) effect of not recognizing
an FB_WRITE as a scheduling barrier even if it was marked EOT --
harmless because the scheduler marked the last instruction of a block as
a barrier, something I'm changing in the following patches.

This will be reimplemented later in the series.