r600g: fix LIT + fix multiple constant one ALU + fix ALU block splitting

r600g: fix LIT + fix multiple constant one ALU + fix ALU block splitting

Make sure LIT fills all slot for instruction (can't do W instruction
without having the Z slot filled with at least a NOP).

ALU instruction can't access more than 4 constant, move constant to
temporary reg if we reach the limit.

Fix ALU block splitting, only split ALU after ALU with last instruction
bit sets.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>