vc4: Replace a magic number with the appropriate #define.

Signed-off-by: Eric Anholt <eric@anholt.net>
vc4: Reenable IRQs in the OOM handler.

Somehow the interrupt enable for OOM gets turned off, which is really
not cool.  This meant a job with multiple bin OOMs would just get
stuck.

Signed-off-by: Eric Anholt <eric@anholt.net>
vc4: Fix decision for whether the TMU-read MIN clamping is to the B file.

Signed-off-by: Eric Anholt <eric@anholt.net>