i965: Drop push-mode reladdr constant loading and always use constant_map.

i965: Drop push-mode reladdr constant loading and always use constant_map.

This eases the gen6 implementation, which can only handle up to 32
registers of constants, while likely not penalizing real apps using
reladdr since all of those I've seen also end up hitting the pull
constant buffer.  On gen6, the constant map means that simple NV VPs
fit under the 32-reg limit and now succeed.  Fixes around 10 testcases.