mesa: change MAX_PROGRAM_ADDRESS_REGS to 1, clamp to it in state tracker

mesa: change MAX_PROGRAM_ADDRESS_REGS to 1, clamp to it in state tracker

We've never properly supported more than one address register.  There
isn't even a field in prog_src_register or prog_dst_register to indicate
which address register to use if RelAddr!=0.

In the state tracker, clamp MaxAddressRegs against MAX_PROGRAM_ADDRESS_REGS
since many gallium drivers do support more.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=65226

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>