r600g: Workaround for a harware bug with nested loops on Cayman

r600g: Workaround for a harware bug with nested loops on Cayman

There is a hardware bug on Cayman where a BREAK/CONTINUE followed by
LOOP_STARTxxx for nested loops may put the branch stack into a state
such that ALU_PUSH_BEFORE doesn't work as expected. Workaround this
by replacing the ALU_PUSH_BEFORE with a PUSH + ALU

Fixes piglit tests EXT_transform_feedback/order*

v2: Use existing loop count and improve comment
v3: [Vadim Girlin] Set jump address for PUSH instructions

NOTE: This is a candidate for the 9.1 branch

Signed-off-by: Vadim Girlin <vadimgirlin@gmail.com>